InfoMagic Standards 1993 July/Disc.iso/ccitt/1988/troff/3_4_11.tro

Text File | 1991-12-12 | 160.7 KB | 7,150 lines

.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\"                 Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
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.ds CH
.ds CF
.EQ
delim @@
.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
.po 4P

.rs
\v | 5i'
.IP
\fB7.4\ Principal characteristics of second order multiplex equipments\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ G.741\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBGENERAL\ CONSIDERATIONS\ ON\ \fR \fBSECOND\ ORDER\ MULTIPLEX\ EQUIPMENTS\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.741''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.741    %'
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1972; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
    The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that different primary and second order multiplex
equipments exist, depending upon the characteristics of different networks
and the various types of signals to be transmitted in those networks;
.PP
(b)
that, although studies will continue with the aim of
reducing the differences between various systems, the existing situation
cannot be changed in the near future;
.sp 1P
.LP
\fIrecommends the following\fR
.sp 9p
.RT
.PP
(1)
when two countries, both using 2048\ kbit/s primary
multiplex equipments such as the PCM multiplex equipment according to
Recommendation\ G.732, have to be connected by a digital path at the second
order bit rate, that bit rate should be 8448\ kbit/s;
.PP
(2)
when two countries, both using 1544\ kbit/s primary
multiplex equipments such as the PCM multiplex equipment according to
Recommendation\ G.733, have to be connected by a digital path at the second
order bit rate, that bit rate should be 6312\ kbit/s.
.PP
In the meantime, it is extremely desirable to define a preferred method
of interconnecting different systems.
.PP
Recommendations\ G.742 and\ G.743 give the characteristics of second
order digital multiplex equipments using positive justification, and
Recommendation\ G.745 gives the characteristics of second order multiplex
equipment using positive/zero/negative justification. Recommendations\ G.744,
G.746 and\ G.747 give the characteristics of second order PCM multiplex
equipments. Paragraphs\ 2 and\ 4 of Recommendation\ G.705 give the characteristics
required to terminate 6312\ kbit/s and 8448\ kbit/s digital paths on a
digital
exchange.
\v'6p'
.RT
.sp 2P
.LP
\fBRecommendation\ G.742\fR
.RT
.sp 2P
.ce 1000
\fBSECOND\ ORDER\ DIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING\ AT\ 8448\ kbit/s\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.742''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.742    %'
.ce 0
.sp 1P
.ce 1000
\fBAND\ USING\ POSITIVE\ JUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1972; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The second order digital multiplex equipment using positive
justification, described below, is intended for use on digital paths between
countries using 2048\ kbit/s primary multiplex equipments.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The nominal bit rate should be 8448\ kbit/s.
.PP
The tolerance on that rate should be \(+- | 0\ parts per
million (ppm).
.bp
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table\ 1/G.742 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the bunched frame alignment signal.
.ce
\fBH.T. [T1.742]\fR
.ce
TABLE\ 1/G.742
.ce
\fB8448\(hykbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    2048
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (1111010000)
 }    1 to 10
.T&
lw(144p) | cw(48p) .
 {
Alarm indication to the remote digital multiplex equipment
 }    11
.T&
lw(144p) | cw(48p) .
Bit reserved for national use    12
.T&
lw(144p) | cw(48p) .
Bits from tributaries    13 to 212
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C\fI\fI
1 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 212
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C\fI\fI
2 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 212
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C\fI\fI
2 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for justification
 }    5 to 8
.T&
lw(144p) | cw(48p) .
Bits from tributaries    9 to 212
_
.T&
lw(144p) | cw(48p) .
Frame length    848 bits
.T&
lw(144p) | cw(48p) .
Bits per tributary    206 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    10 kbit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.424
.TE
.LP
\fINote\fR
\ \(em\ C
\fIj\fR
\fIi\fR
indicates the \fIi\fR
th justification
control bit of the \fIj\fR
th tributary.
.nr PS 9
.RT
.ad r
\fBTable 1/G.742 [T1.742], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame alignment and consequent action\fR
.sp 1P
.RT
.PP
Loss of frame alignment should be assumed to have taken place when four
consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
When frame alignment is assumed to be lost, the frame alignment device
should decide that such alignment has effectively been recovered when it
detects the presence of three consecutive frame alignment signals.
.PP
The frame alignment device having detected the appearance of a single correct
frame alignment signal, should begin a new search for the frame
alignment signal when it detects the absence of the frame alignment signal
in one of the two following frames.
.PP
\fINote\fR \ \(em\ As it is not strictly necessary to specify the detailed
frame alignment strategy, any suitable frame alignment strategy may be
used provided the performance achieved is at least as efficient in all
respects as that
obtained by the above frame alignment strategy.
.bp
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing method\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification is recommended.
.PP
The justification control signal should be distributed and use the
C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits (\fIn\fR \ =\ 1, 2, 3, see Table\
1/G.742).
.PP
Positive justification should be indicated by the signal\ 111, no
justification by the signal\ 000. Majority decision is recommended.
.PP
Table\ 1/G.742 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.sp 2P
.LP
\fB6\fR     \fBJitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
    \fIJitter transfer characteristic\fR
.sp 9p
.RT
.PP
A 2048\ kbit/s signal, modulated by sinusoidal jitter, should be
subject to a muldex jitter transfer characteristic within the gain/frequency
limits given in Figure\ 1/G.742. The equivalent binary content of the test
signal should be\ 1000.
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure 1/G.742, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.2
    \fITributary output jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at a tributary output in the absence of
input jitter should not exceed 0.25\ UI when measured in the frequency
range up to\ 100\ kHz.
.PP
When measured with an instrument incorporating a bandpass filter
having a lower cutoff frequency of 18\ kHz, a roll\(hyoff of 20\ dB/decade and
an upper limit of 100\ kHz, the peak\(hyto\(hypeak output jitter should
not exceed
0.05\ UI with a probability of 99.9% during a measurement period of 10\ s.
.PP
\fINote\fR \ \(em\ For interfaces meeting the national high Q\ option,
detailed in Recommendation\ G.703, the lower cutoff frequency for the above
measurement should be 700\ Hz.
.bp
.RT
.sp 1P
.LP
6.3
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
In the case where the transmitting timing signal is derived from an internal
oscillator, the peak\(hyto\(hypeak jitter at the 8448\ kbit/s output should
not exceed 0.05\ UI when it is measured within the frequency range from
\fIf\fR\d1\u\ =\ 20\ Hz to \fIf\fR\d4\u\ =\ 400\ kHz.
.RT
.sp 2P
.LP
\fB7\fR     \fBDigital interfaces\fR
.sp 1P
.RT
.PP
The digital interfaces at 2048\ kbit/s and 8448\ kbit/s should be in accordance
with Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexer timing signal from an external source as well as from an
internal source.
.RT
.sp 2P
.LP
\fB9\fR     \fBService digits\fR
.sp 1P
.RT
.PP
Two bits per frame are available for service functions. Bit\ 11 of Set\
I is used to transmit an alarm indication to the remote multiplex equipment
when specific fault conditions are detected in the multiplex equipment
(see
\(sc\ 10 below). Bit\ 12 of Set\ I is reserved for national use. On the
digital path crossing the border, this bit is fixed at\ 1.
.RT
.sp 2P
.LP
\fB10\fR     \fBFault conditions\fR \fBand consequent conditions\fR
.sp 1P
.RT
.sp 1P
.LP
10.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The digital multiplex equipment should detect the following fault   conditions:
.RT
.PP
10.1.1
Failure of power supply.
.sp 9p
.RT
.PP
10.1.2
Loss of an incoming signal at 2048\ kbit/s at the input of the   multiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ Where separate circuits are used for the digital signal
and the timing signal then loss of either or both should constitute loss
of the incoming signal.
.PP
10.1.3
Loss of the incoming signal at 8448\ kbit/s at the input of the  demultiplexer.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The detection of this fault condition is required
only when it does not result in an indication of loss of frame alignment.
.PP
\fINote\ 2\fR \ \(em\ Where separate circuits are used for the digital
signal and the timing signal, then loss of either or both should constitute
loss of the
incoming signal.
.RT
.PP
10.1.4
Loss of frame alignment.
.sp 9p
.RT
.PP
10.1.5
Alarm indication received from the remote multiplex equipment at the 8448\
kbit/s input of the demultiplexer (see \(sc\ 10.2.2 below).
.sp 9p
.RT
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to the detection of a fault condition, appropriate actions should
be taken as specified by Table\ 2/G.742. The consequent actions are as
follows:
.RT
.PP
10.2.1
Prompt maintenance alarm indication generated to signify that performance
is below acceptable standards and maintenance attention is
required locally. When the Alarm Indication Signal (AIS) (see Note\ 2
under \(sc\ 10.2.5 below) at 8448\ kbit/s is detected at the input of the
demultiplexer, the prompt maintenance alarm indication associated with
loss of frame alignment should be inhibited, while the rest of the consequent
actions are in accordance with those associated in Table\ 2/G.742 with
the fault
condition.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarm activated by this maintenance alarm indication is left to the discretion
of each Administration.
.PP
10.2.2
Alarm indication to the remote multiplex equipment generated by changing
from the state\ 0 to the state\ 1\ bit\ 11 of Set\ I at the 8448\ kbit/s
output of the multiplexer.
.bp
.sp 9p
.RT
.PP
10.2.3
AIS (see Notes\ 1 and\ 2 below) applied to all four
2048\ kbit/s tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
10.2.4
AIS (see Notes\ 1 and\ 2 below) applied to the 8448\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
10.2.5
AIS (see Note\ 2 below) applied to the time slots of the
8448\ kbit/s signal at the output of the multiplexer, corresponding to the
relevant 2048\ kbit/s tributary.
.sp 9p
.RT
.PP
The method of transmitting the AIS at the output port of the
multiplexer in time slots corresponding to a faulty input tributary, should
be such that the status of the justification control digits is controlled
so as to ensure that the AIS is within the tolerance specified for that
tributary.
.ce
\fBH.T. [T2.742]\fR
.ce
TABLE\ 2/G.742
.ce
\fBFault conditions and consequent actions\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part     {
Fault condition
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplex equipment generated
 }    AIS applied     To all the tributaries    To the composite signal      {
To the
relevant time slots of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure of power supply    Yes        Yes, if practicable    Yes, if practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 8448 kbit/s
 }    Yes    Yes    Yes    Loss of frame alignment     Yes
    Yes    Yes     {
Alarm indication received from the
remote multiplex
equipment
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTable 2/G.742 [T2.742], p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output
of the multiplexer equipment or at the output of the demultiplexer equipment
should be in accordance with the interface specifications.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the
AIS at 2048\ kbit/s and 8448\ kbit/s is nominally a continuous stream of\ 1s.
The strategy for detecting the presence of the AIS should be such that
the AIS is detectable even in the presence of an error ratio\ 1 | (mu | 0\uD\dlF261\u3\d.
However, a signal, with all bits except the frame alignment signal in the
1s\ state, should not be mistaken for an AIS.
.RT
.sp 1P
.LP
10.3
    \fITime requirements\fR
.sp 9p
.RT
.PP
The fault detection and the application of the consequent actions listed
in \(sc\(sc\ 10.2.2 to\ 10.2.5, including the detection of AIS, should
be
completed within a time limit of 1\ ms.
.bp
.RT
.sp 2P
.LP
\fBRecommendation\ G.743\fR
.RT
.sp 2P
.ce 1000
\fBSECOND\ ORDER\ DIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING\ AT\ 6312\ kbit/s\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.743''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.743    %'
.ce 0
.sp 1P
.ce 1000
\fBAND\ USING\ POSITIVE\ JUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1972; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The second order digital multiplex equipment using positive
justification described below, is intended for use on digital paths between
countries using 1544\ kbit/s primary multiplex equipments.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The nominal bit rate should be 6312\ kbit/s.
.PP
The tolerance on that rate should be \(+- | 0\ parts per million
(ppm).
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table\ 1/G.743 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the distributed frame and multiframe alignment
signals.
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame and multiframe alignment and
consequent action\fR
.sp 1P
.RT
.PP
The frame alignment recovery time should not exceed 16\ ms. The
signal to be applied to the tributaries during the out\(hyof\(hyframe\(hyalignment
time should be studied.
.PP
Once frame alignment is established, multiframe alignment should be
recovered in less than 420\ micro
seconds.
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing method\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification is recommended.
.PP
The justification control signal should be distributed and use the
C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits (\fIn\fR \ =\ 1, 2, 3, see Table\
1/G.743).
.PP
Positive justification should be indicated by the signal\ 111, no
justification by the signal\ 000. Majority decision is recommended.
.PP
Table\ 1/G.743 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.sp 2P
.LP
\fB6\fR     \fBJitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
    \fISpecifications at the input ports\fR
.sp 9p
.RT
.PP
The digital signal presented at the input ports shall be as defined in
Recommendation\ G.703 modified by the transmission characteristic of the
interconnecting cable. The input ports shall be able to tolerate a digital
signal with these electrical characteristics but modified by sinusoidal
jitter up to the limits specified by the amplitude frequency relationship
in
Figure\ 1/G.743. The equivalent binary content of the signal, with jitter
modulation, applied to the inputs shall be a pseudo\(hyrandom bit sequence of
length\ 2\u1\d\u5\d\ \(em\ 1.
.PP
\fINote\fR \ \(em\ The signal with jitter modulation applied to the
demultiplexer input shall contain the bits necessary for framing and
justification in addition to information bits.
.bp
.RT
.ce
\fBH.T. [T1.743]\fR
.ce
TABLE\ 1/G.743
.ce
\fB6312\(hykbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    1544
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
 {
Frame structure (see Notes\ 1 and 2)
 }    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Bit for multiframe alignment signal (M
\fIj\fR
) (see Note\ 1)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 49
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
1st bit for justification control signal
(C
\fIj\fR
1)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 49
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
1st bit for frame alignment signal (F
0)
(see Note\ 3)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 49
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
2nd bit for justification control signal (C
\fIj\fR
2)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 49
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
3rd bit for justification control signal (C
\fIj\fR
3)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 49
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
2nd bit for frame alignment signal (F
1)
(see Note\ 3)
 }    1
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries (see Note\ 4)
 }    2 to 49
_
.T&
lw(144p) | cw(48p) .
Frame length    \ 294 bits
.T&
lw(144p) | cw(48p) .
Multiframe length    1176 bits
.T&
lw(144p) | cw(48p) .
 {
Bits per tributary per multiframe (including justification)
 }    \ 288 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    5367 bit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.334
.TE
.LP
\fINote\ 1\fR
\ \(em\ This frame is repeated 4 times to form a multiframe with designated \fIj\fR
 |  | , 2, 3 , 4. The multiframe alignment signal is a 011\fIx\fR
\(hypattern. \fIx\fR
may be used as an alarm service digit.
.LP
\fINote\ 2\fR
\ \(em\ The bits from the second and fourth tributaries are inverted
logically
before multiplexing with the bits from the first and third tributaries.
.LP
\fINote\ 3\fR
\ \(em\ The frame alignment is F
0 |  |  and F
1 |  | .
.LP
\fINote\ 4\fR
\ \(em\ The bit available for the justification of tributary \fIj\fR
is the
first time slot of tributary \fIj\fR
following F
1 in the \fIj\fR
th frame.
.nr PS 9
.RT
.ad r
\fBTable 1/G.743 [T1.743], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 23P
.ad r
\fBFigure 1/G.743 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.2
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
The jitter at the 6312\ kbit/s output of the multiplexer should not exceed
0.01\ UI\ rms.
.RT
.sp 1P
.LP
6.3
     \fIDemultiplexer output jitter with no multiplexer or demultiplexer\fR
\fIinput jitter\fR
.sp 9p
.RT
.PP
With no jitter at the input to the multiplexer and demultiplexer, the jitter
at the demultiplexer output should not exceed 1/3\ unit\ intervals
peak\(hyto\(hypeak.
.RT
.sp 1P
.LP
6.4
    \fIDemultiplexer jitter transfer characteristic\fR
.sp 9p
.RT
.PP
The gain of the jitter transfer characteristic should not exceed
the limits given in Figure\ 2/G.743.
.RT
.LP
.rs
.sp 15P
.ad r
\fBFigure 2/G.743, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB7\fR     \fBDigital interfaces\fR
.sp 1P
.RT
.PP
The digital interfaces at 1544\ kbit/s and 6312\ kbit/s should be in accordance
with Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexer timing signal from an external source as well as from an
internal source.
.RT
.sp 2P
.LP
\fB9\fR     \fBService digits\fR
.sp 1P
.RT
.PP
The service digits are reserved for national use.
.RT
.sp 2P
.LP
\fB10\fR     \fBFault conditions\fR \fBand consequent actions\fR
.sp 1P
.RT
.sp 1P
.LP
10.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The digital multiplex equipment should detect the following fault   conditions.
.RT
.PP
10.1.1
Failure of power supply.
.PP
10.1.2
Loss of frame alignment at the demultiplexer.
.PP
It may also be equipped to detect the following fault conditions.
.PP
10.1.3
Loss or degradation of incoming 1544\ kbit/s signal.
.PP
10.1.4
Loss or degradation of incoming 6312\ kbit/s signal.
.PP
10.1.5
Failure of the multiplex or demultiplex as evidenced by
incorrect multiplexing or demultiplexing action.
.PP
10.1.6
Failure of standby (if the multiplex is so equipped).
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
On the detection of a fault condition, the following appropriate
actions should be taken:
.RT
.PP
10.2.1
For a multiplex equipped with automatic changeover, the
consequent actions are specified in
Table\ 2/G.743. For a multiplex so
equipped, a switch to a standby is performed in the event of a failure
of the multiplex equipment in service. A maintenance alarm is generated
if a switch
takes place, or if the standby fails. A prompt maintenance alarm is generated
if an incoming signal fails, or if service is lost due to inability to
complete automatic changeover to the standby.
.PP
10.2.2
For a multiplex not equipped with automatic changeover, a
prompt maintenance alarm is generated in response to any fault condition
detected. Such multiplexers will normally be equipped to detect power failure
and loss or degradation of incoming signal at the demultiplexer.
.PP
10.2.3
The provision of an Alarm Indication Signal (AIS) to the
1544\ kbit/s tributary outputs from the demultiplexer is under study. An AIS,
suitable for use without special detectors at the primary PCM multiplex
might be provided on an optional basis.
.LP
.rs
.sp 10P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.743]\fR
.ce
TABLE\ 2/G.743
.ce
\fBFault conditions and consequent actions for a multiplex equipped with
.ce
automatic changeover\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(48p) | cw(36p) sw(36p) sw(36p) sw(36p) , ^  | ^  | c | c | c | l.
Equipment part     {
Fault condition
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2.1)
Prompt maintenance alarm indication generated
 }
         {
Deferred maintenance alarm indication generated
 }     {
Alarm indication
to the remote multiplex equipment generated
(if so equipped)
 }     {
Automatic changeover
actuated
 }
_
.T&
lw(36p) | lw(48p) | cw(36p) | cw(36p) | lw(36p) | cw(36p) .
Multiplexer demultiplexer    Failure  of power supply    No    Yes        Yes
_
.T&
lw(36p) | lw(48p) | cw(36p) | cw(36p) | lw(36p) | cw(36p) .
Multiplexer only     {
Loss or degradation of incoming signal
on a tributary
 }    Yes            No
_
.T&
lw(36p) | lw(48p) | cw(36p) | cw(36p) | cw(36p) | lw(36p) , ^  | c | l | l | l | l.
Demultiplexer only     {
Loss or degradation of incoming signal
at 6312 kbit/s
 }    Yes    Yes    No     {
Alarm indication received from the remote multiplex equipment
(if so equipped)
 }
    Yes
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTableau 2/G.743 [T2.743], p. 7\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBRecommendation\ G.744\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBSECOND\ ORDER\ PCM\ MULTIPLEX\ EQUIPMENT\ OPERATING\ AT\ 8448\ kbit/s\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.744''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.744    %'
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; amended at Geneva, 1980 and at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral characteristics\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
    \fIFundamental characteristics\fR
.sp 9p
.RT
.PP
The encoding law used is the A\(hylaw as specified in
Recommendation\ G.711. The sampling rate, load capacity and the code are also
specified in that Recommendation.
.PP
The number of quantized values is 256.
.PP
\fINote\fR \ \(em\ The inversion of bits\ 2, 4, 6 and 8 is covered by the
encoding law and is applicable only to voice\(hychannel time slots.
.bp
.RT
.sp 1P
.LP
1.2
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate is 8448\ kbit/s. The tolerance on this rate is \(+- | 0\
parts per million (ppm).
.RT
.sp 1P
.LP
1.3
    \fITiming signal\fR
.sp 9p
.RT
.PP
It should be possible to derive the transmitting timing signal of a PCM
multiplex equipment from an internal source, from the incoming digital
signal and also from an external source.
.PP
\fINote\fR \ \(em\ Further study is required on the effect of jitter of the
incoming signal on the timing signal, and on the measures to be taken in
case of loss of the incoming signal or the external source.
.RT
.sp 2P
.LP
\fB2\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Refer to \(sc\(sc 3.4.1 and 3.4.2 of Recommendation G.704 for frame
structure and use of derived channel time slots.
.RT
.sp 2P
.LP
\fB3\fR     \fBLoss and recovery of frame alignment\fR
.sp 1P
.RT
.PP
Loss of frame alignment should be assumed to have taken place when four
consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
When frame alignment is assumed to be lost, the frame alignment device
should decide that such alignment has effectively been recovered when it
detects the presence of three consecutive frame alignment signals.
.PP
The frame alignment device having detected the appearance of a single correct
frame alignment signal, should begin a new search for the frame
alignment signal when it detects the absence of the frame alignment signal
in one of the two following frames.
.RT
.sp 2P
.LP
\fB4\fR     \fBFault conditions\fR \fBand consequent actions\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The PCM multiplex equipment should detect the following fault
conditions.
.RT
.PP
4.1.1
Failure of power supply.
.sp 9p
.RT
.sp 1P
.LP
4.1.2
    \fIFailure of codec (except when using single\(hychannel codecs)\fR
.sp 9p
.RT
.PP
As a minimum requirement, this fault condition should be recognized when,
for at least one signal level in the range \(em21\ to \(em6\ dBm0, the
signal\(hyto\(hyquantizing noise ratio performance of the local codec is
18\ dB or
more below the level recommended in Recommendation\ G.712.
.RT
.sp 1P
.LP
4.1.3
    \fILoss of incoming signal at the 64 kbit/s input port\fR
\fI(time slots 67 to 70)\fR
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The detection of this fault condition is not mandatory
when channel associated signalling is used and the signalling multiplex
is
situated within a few metres of the PCM multiplex equipment.
.PP
\fINote\ 2\fR \ \(em\ The detection of this fault condition is not mandatory
when contradirectional interfaces are used.
.RT
.PP
4.1.4
Loss of the incoming signal at 8448\ kbit/s.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The detection of this fault condition is required
only when it does not result in an indication of loss of frame alignment.
.PP
\fINote\ 2\fR \ \(em\ Where separate circuits are used for the digital
signal and the timing signal, then loss of either or both should constitute
loss of the
incoming signal.
.bp
.RT
.PP
4.1.5
Loss of frame alignment.
.sp 9p
.RT
.PP
4.1.6
Excessive bit error ratio detected by monitoring the frame
alignment signal.
.sp 9p
.RT
.PP
4.1.6.1
With a random bit error of \(= | 0\uD\dlF261\u4\d, the probability of
activating the indication of fault condition within a few seconds should be
less than\ 10\uD\dlF261\u6\d.
.PP
With a random bit error of \(>="\ 10\uD\dlF261\u3\d, the probability of
activating the indication of fault condition within a few seconds should be
higher than\ 0.95.
.PP
4.1.6.2
With a random bit error ratio of \(>=" | 0\uD\dlF261\u3\d, the
probability of deactivating the indication of fault condition within a few
seconds should be almost\ 0.
.PP
With a random bit error of \(>="\ 10\uD\dlF261\u4\d, the probability of
deactivating the indication of fault condition within a few seconds should
be higher than\ 0.95.
.PP
\fINote\fR \ \(em\ The activating and the deactivating period specified as
\*Qa few seconds\*U is intended to be in the order of 4 to 5\ seconds.
.RT
.PP
4.1.7
Alarm indication received from the remote end (see
\(sc\ 4.2.3 below).
.sp 9p
.RT
.sp 1P
.LP
4.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to the detection of a fault condition, appropriate actions should
be taken as specified in Table\ 1/G.744. The consequent actions are as
follows:
.RT
.PP
4.2.1
Service alarm indication generated to signify that the
service provided by the PCM multiplex is no longer available. This indication
should be forwarded at least to the switching and/or signalling multiplex
equipment depending upon the arrangements provided. The indication should be
given as soon as possible and not later than 2\ ms after detection of the
relevant fault condition.
.sp 9p
.RT
.PP
This specification, taking into account the specification given in \(sc\
3 above, is equivalent to recommending that the average time to detect
a
loss of frame alignment or a loss of the incoming 8448\(hykbit/s signal and to
give the relevant indication should not be greater than 3\ ms.
.PP
When using common channel signalling, the indication should be
forwarded to the switching equipment by means of a separate interface on the
PCM multiplex equipment.
.RT
.PP
4.2.2
Prompt maintenance alarm indication generated to signify
that performance is below acceptable standards and maintenance attention is
required locally. When the Alarm Indication Signal (AIS) (see General Note
below to \(sc\ 4.2) is detected the prompt maintenance alarm indication,
associated with loss of frame alignment (see \(sc\ 4.1.5 above) and excessive
error rate (see \(sc\ 4.1.6 above), should be inhibited, while the rest
of the consequent actions are in accordance with those associated in Table\
1/G.744 with the two fault
conditions.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarms activated by the alarm indications given in \(sc\(sc\ 4.2.1 and\
4.2.2, is left to the discretion of each Administration.
.PP
4.2.3
Alarm indication to the remote end generated by changing bit\ 7 of channel
time slot\ 66 from the state\ 0 to the state\ 1. This should be
effected as soon as possible.
.sp 9p
.RT
.PP
4.2.4
Transmission suppressed at the analogue outputs.
.sp 9p
.RT
.PP
4.2.5
AIS applied to time slots 67 to 70 of the 64\ kbit/s outputs
when not used for speech (see General Note below to \(sc\ 4.2). This action
should be taken as soon as possible and not later than 2\ ms after the
detection of the fault condition.
.sp 9p
.RT
.PP
4.2.6
AIS applied to time slots 67 to 70 of the output 8448\ kbit/s
composite signal when these are not used for speech (if supervision of
incoming 64\ kbit/s signal is provided).
.sp 9p
.RT
.PP
\fIGeneral Note to \(sc\ 4.2\fR \ \(em\ The equivalent binary content of
the AIS is a continuous stream of binary\ 1s.
.PP
The strategy for detecting the presence of the AIS should be such that
the AIS is detectable, even in the presence of an error ratio\ 1 | (mu | 0\uD\dlF261\u3\d.
However, a signal with all bits except the frame alignment in the 1s\ state,
should not be mistaken for an AIS.
.PP
\fINote\fR \ \(em\ All timing requirements quoted apply equally to
restoration, subsequent to the fault condition clearing.
.bp
.RT
.ce
\fBH.T. [T1.744]\fR
.ce
TABLE\ 1/G.744
.ce
\fBFault conditions and consequent actions for the PCM multiplex
.ce
equipment
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(54p) | cw(24p) sw(24p) sw(24p) sw(24p) sw(24p) sw(24p) , ^  | ^  | c | c | c | c | c | l.
Equipment part     {
Fault condition
(see \(sc\ 4.1)
 }     {
Consequent action (see \(sc\ 4.2)
Service alarm indication generated
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication
to the
remote end generated
 }     {
Transmission suppressed
at the analogue outputs
 }     {
AIS applied to 64\(hykbit/s outputs (time slots 67 to 70)
 }     {
AIS applied to time slots 67 to 70
of the
8448 kbit/s composite
signal
 }
_
.T&
lw(30p) | lw(54p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | l | c | c | c | c | l | l.
Multiplexer and demultiplexer    Failure  of power supply    Yes    Yes    Yes, if practicable    Yes, if practicable    Yes, if practicable    Yes, if practicable
    Failure of codec    Yes    Yes    Yes    Yes
_
.T&
lw(30p) | lw(54p) | lw(24p) | cw(24p) | lw(24p) | lw(24p) | lw(24p) | cw(24p) .
Multiplexer only     {
Loss of incoming signal
at 64\(hykbit/s inputs time slots 67 to 70
(see notes under \(sc\ 4.1.3)
 }        Yes                Yes
_
.T&
lw(30p) | lw(54p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | lw(24p) , ^  | c | c | c | c | c | l | c
^  | c | c | c | c | l | c | l
^  | l | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming
signal at 8448 kbit/s
 }    Yes    Yes    Yes    Yes    Yes    Loss of frame alignment
    Yes    Yes    Yes    Yes    Yes     {
Error rate 1 in 10\uD\dlF261\u3\d
for the alignment signal
 }    Yes    Yes    Yes    Yes    Yes     {
Alarm indication received from the remote end
(bit 7 of time
slot 66)
 }    Yes
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTable 1/G.744 [T1.744], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB5\fR     \fBSignalling\fR
.sp 1P
.RT
.sp 1P
.LP
5.1
    \fISignalling arrangement\fR
.sp 9p
.RT
.PP
Refer to \(sc 3.4.3 of Recommendation G.704. Channel time\(hyslots\ 67
to\ 70 may be used to provide an interface at 64\ kbit/s which shall be
suitable for use with either common channel or channel\(hyassociated signalling
or other
services as required.
.RT
.sp 1P
.LP
5.2
    \fILoss and recovery of multiframe alignment in case of\fR
\fIchannel\fR \fIassociated signalling\fR
.sp 9p
.RT
.PP
For multiframe alignment each 64\ kbit/s channel should be treated separately.
For each channel, multiframe alignment should be assumed to have
been lost when two consecutive multiframe alignment signals have been received
with an error.
.bp
.PP
Multiframe alignment should be assumed to have been recovered as soon as
the first correct multiframe signal is detected.
.PP
\fINote\fR \ \(em\ To avoid a condition of spurious multiframe alignment, the
following procedure may be used, in addition to the above:
.RT
.LP
    \(em
    Multiframe alignment should be assumed to have been lost
when, for a period of one or two multiframes, all the bits in
the relevant channel time slots\ 67, 68, 69 or\ 70 are at the
state\ 0.
.LP
    \(em
    Multiframe alignment should be assumed to have been
recovered, only when at least one bit in the state\ 1 is present
in the relevant time slots 67, 68, 69 or\ 70 preceding the
multiframe alignment signal first detected.
.sp 1P
.LP
5.3
    \fIFault conditions and consequent actions in case of channel\fR
\fIassociated signalling\fR
.sp 9p
.RT
.PP
The fault conditions and consequent actions for each 64\ kbit/s
signalling channel and for each signalling multiplex equipment are the
same as recommended in Recommendation\ G.732, \(sc\ 5.3.
.RT
.sp 2P
.LP
\fB6\fR     \fBInterfaces\fR
.sp 1P
.RT
.PP
The analogue interfaces should be in accordance with
Recommendations\ G.712, G.713 and G.714. The digital interfaces at 8448\
kbit/s should be in accordance with Recommendation\ G.703. The digital
interfaces at
64\ kbit/s should be of either the codirectional or the contradirectional
type specified in Recommendation\ G.703. The specifications for 64\ kbit/s
interfaces are not mandatory for channel associated signalling.
.RT
.sp 2P
.LP
\fB7\fR     \fBJitter\fR
.sp 1P
.RT
.sp 1P
.LP
7.1
    \fIMultiplex signal output jitter at 8448\ kbit/s output\fR
.sp 9p
.RT
.PP
In the case where the transmitting timing signal is derived from an internal
oscillator, the peak\(hyto\(hypeak jitter at the 8448\ kbit/s output should
not exceed 0.05\ UI when it is measured within the frequency range from
\fIf\fR\d1\u\fR \ =\ 20\ Hz to\ \fIf\fR\d4\u\ =\ 400\ kHz.
.RT
.sp 2P
.LP
7.2
    \fIJitter at 64\ kbit/s output\fR (for interfaces according to Rec.
G.703)
.sp 1P
.RT
.PP
7.2.1
In the case where the incoming 8448 kbit/s signal has no jitter, the peak\(hyto\(hypeak
jitter at the 64\ kbit/s output should not exceed 0.025\ UI when it is
measured within the frequency range from\ \fIf\fR\d1\u\ =\ 20\ Hz
to\ \fIf\fR\d4\u\ =\ 10\ kHz. The equivalent binary content of the test
signal applied to the 8448\ kbit/s input shall be a pseudo\(hyrandom bit
sequence of
length\ 2\u1\d\u5\d\(em1 as specified in Recommendation\ O.151.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ In order to carry out this measurement without invoking
AIS at the 64\ kbit/s output, it will normally be necessary to include
a frame alignment signal in the test signal.
.PP
7.2.2
The jitter transfer function between the 8448\ kbit/s input and the 64\
kbit/s output is under study.
.sp 9p
.RT
.sp 2P
.LP
\fBRecommendation\ G.745\fR
.RT
.sp 2P
.ce 1000
\fBSECOND\ ORDER\ DIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING\ AT\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.745''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.745    %'
.ce 0
.sp 1P
.ce 1000
\fB8448\ kbit/s\ AND\ USING\ POSITIVE/ZERO/NEGATIVE\ JUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; amended at Geneva, 1980 and at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The second order digital multiplex equipment using
positive/zero/negative justification, considered below, is intended for
use on digital paths between countries using 2048\ kbit/s primary multiplex
equipments, such as the PCM\ multiplex equipment described in Recommendation\
G.732 or any
identical equipment.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The nominal bit rate should be 8448 kbit/s. The tolerance on that rate
should be \(+- | 0\ parts per million\ (ppm).
.bp
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table 1/G.745 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the bunched frame alignment signal.
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame alignment and consequent action\fR
.sp 1P
.RT
.PP
Loss of frame alignment should be assumed to have taken place when five
consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
Recovery of frame alignment should take place in the case of receiving
without errors at least two consecutive frame signals in their predicted
positions.
.PP
As soon as frame alignment has been lost and until it has been
recovered, a definite pattern should be sent to all tributaries from the
output of the demultiplexer. The equivalent binary content of this pattern,
called the Alarm Indication Signal\ (AIS), at 2048\ kbit/s is a continuous
stream of
binary\ 1s.
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing method\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive/zero/negative justification with two\(hycommand control are
recommended.
.PP
The justification control signal should be distributed and use the
C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits (\fIn\fR \ =\ 1, 2, 3, see Table\
1/G.745). Correction of one error in command is possible.
.PP
Positive justification should be indicated by the signal 111,
transmitted in each of two consecutive frames; negative justification should
be indicated by the signal\ 000 transmitted in each of two consecutive
frames, and no justification by the signal\ 111 in one frame followed by\
000 in the next
frame. Bits\ 5, 6, 7 and\ 8 in Set\ IV (see Table\ 1/G.745) are used for
negative justification of tributaries\ 1, 2, 3 and\ 4 respectively, and
bits\ 9 to\ 12 for positive justification of the same tributaries.
.PP
Besides, when information from tributaries\ 1, 2, 3 and\ 4 is not
transmitted, bits\ 5, 6, 7 and\ 8 in Set\ IV are available for transmitting
information concerning the type of justification (positive or negative) in
frames containing commands of positive justification control and intermediate
amount of jitter in frames containing commands of negative justification.
.PP
Table 1/G.745 gives the maximum justification rate per
tributary.
.RT
.sp 2P
.LP
\fB6\fR     \fBJitter\fR
.sp 1P
.RT
.PP
The amount of jitter that should be tolerated at the input of the multiplexer
and the demultiplexer should be according to Rec.\ G.823, \(sc\ 3.1.1.
The amount of jitter at the output of the multiplexer and the
demultiplexer should be studied and specified.
.RT
.sp 2P
.LP
\fB7\fR     \fBDigital interface\fR
.sp 1P
.RT
.PP
The digital interfaces at 2048 kbit/s and 8448 kbit/s should be in accordance
with Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
It might be desirable to be able to derive the multiplexer timing signal
from an external source as well as from an internal one.
.RT
.sp 2P
.LP
\fB9\fR     \fBService digits\fR
.sp 1P
.RT
.PP
Some spare bits per frame are available for service functions (bits from\
5 to\ 8 in Set\ II and bit\ 8 in Set\ III) for national and international
use. Bits\ 5, 6, 7 and\ 8 in Set\ II are available for a digital service
channel
between two terminals (using 32\ kbit/s Adaptive Delta Modulation) and
bit\ 8 in Set\ III is available for ringing up a digital service channel.
Utilization of other spare bits is under study.
.bp
.RT
.ce
\fBH.T. [T1.745]\fR
.ce
TABLE\ 1/G.745
.ce
\fB8448\(hykbit/s digital multiplexing frame structure using
.ce
positive/zero/negative justification
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    2048
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (11100110)
 }    1 to 8
.T&
lw(144p) | cw(48p) .
Bits from tributaries    9 to 264
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C\fI\fI
1 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits for service functions    5 to 8
.T&
lw(144p) | cw(48p) .
Bits from tributaries    9 to 264
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C\fI\fI
2 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Spare bits    5 to 8
.T&
lw(144p) | cw(48p) .
Bits from tributaries    9 to 264
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C\fI\fI
3 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for negative justification
 }    5 to 8
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for positive justification
 }    9 to 12
.T&
lw(144p) | cw(48p) .
Bits from tributaries    12 to 264
_
.T&
lw(144p) | cw(48p) .
Frame length    1056 bits
.T&
lw(144p) | cw(48p) .
Frame duration    125 \(*ms
.T&
lw(144p) | cw(48p) .
Bits per tributary    256 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    8 kbit/s
.TE
.LP
\fINote\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates \fIn\fR
th justification control
bit of the \fIj\fR
th tributary.
.nr PS 9
.RT
.ad r
\fBTable 1/G.745  [T1.745], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB10\fR     \fBFault conditions\fR \fBand consequent actions\fR
.sp 1P
.RT
.PP
10.1
The digital multiplex equipment should detect the following
fault conditions:
.sp 9p
.RT
.PP
10.1.1
Failure of power supply.
.sp 9p
.RT
.PP
10.1.2
Loss of incoming signal at 2048\ kbit/s at the input of the
multiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ When using separate circuits for the digital signal
and the timing signal, loss of either or both should constitute loss of
the
incoming signal.
.PP
10.1.3
Loss of the incoming signal at 8448\ kbit/s at the input of the  demultiplexer.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The detection of this fault condition is required
only when it does not result in an indication of loss of frame alignment.
.PP
\fINote\ 2\fR \ \(em\ When using separate circuits for the digital signal
and the timing signal, loss of either or both should constitute loss of
the incoming
signal.
.RT
.PP
10.1.4
Loss of frame alignment.
.sp 9p
.RT
.PP
10.1.5
Alarm indication received from the remote multiplex equipment at the 8448\
kbit/s input of the demultiplexer (see \(sc\ 10.2.2).
.bp
.sp 9p
.RT
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
After detection of a fault condition appropriate actions should be taken
as specified in Table\ 2/G.745. The consequent actions are as
follows:
.RT
.PP
10.2.1
Prompt maintenance alarm indication generated to
designate that the performance is below acceptable standards and maintenance
attention is required locally. When detecting the AIS at the 8448\ kbit/s
input of the demultiplexer, the prompt maintenance alarm indication associated
with loss of frame alignment should be prohibited (see Note\ 1 below).
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarm activated by this prompt maintenance alarm indication is left to
the
discretion of each Administration.
.PP
10.2.2
Alarm indication to the remote multiplex equipment generated by changing
from the state\ 0 to the state\ 1\ bit\ 7 of set\ III at the 8448\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
10.2.3
AIS (see Note 2 below) applied to all the four 2048\ kbit/s
tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
10.2.4
AIS (see Note 2 below) applied to the 8448\ kbit/s output of the multiplexer.
.sp 9p
.RT
.PP
10.2.5
AIS (see Note 2 below) applied to the time slots of the
8448\ kbit/s signal at the multiplexer output corresponding to the relevant
2048\ kbit/s tributary.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output of the
corresponding demultiplexer should be as specified for the tributaries. The
method of achieving this is under study.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the AIS at 2048\
kbit/s and 8448\ kbit/s is a continuous stream of binary\ 1s.
.RT
.ce
\fBH.T. [T2.745]\fR
.ce
TABLE\ 2/G.745
.ce
\fBFault conditions and consequent actions\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part     {
Fault condition
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplexer generated
 }    AIS applied    To all the tributaries    To the composite signal      {
To the relevant time slots
of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes    Yes, si practicable    Yes, si practicable    Yes, si practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 8448 kbit/s
 }    Yes    Yes    Yes    Loss of frame alignment    Yes
    Yes    Yes     {
AIS received from
the remote multiplexer
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTable 2/G.745 [T2.745], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ G.746\fR
.RT
.sp 2P
.ce 1000
\fBCHARACTERISTICS\ OF\ SECOND\ ORDER\ PCM\ MULTIPLEX\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.746''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.746    %'
.ce 0
.sp 1P
.ce 1000
\fBEQUIPMENT\ OPERATING\ AT\ 6312\ kbit/s\fR
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral characteristics\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
    \fIFundamental characteristics\fR
.sp 9p
.RT
.PP
The encoding law used is the \(*m\(hylaw as specified in
Recommendation\ G.711. The sampling rate, load capacity and the code are also
specified in that Recommendation.
.PP
The number of quantized values is 255. Two character signals are
reserved for zero value (11111111 and 01111111).
.PP
In some networks the all 0 character signal (00000000) is eliminated to
avoid loss of timing information to the digital line, resulting in
254\ quantized values.
.RT
.sp 1P
.LP
1.2
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate is 6312 kbit/s. The tolerance on this rate is \(+- | 0
parts per million (ppm).
.RT
.sp 1P
.LP
1.3
    \fITiming signal\fR
.sp 9p
.RT
.PP
It should be possible to derive the transmitting timing signal of a PCM
multiplex equipment from an internal source, from the incoming digital
signal and also from an external source.
.RT
.sp 2P
.LP
\fB2\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Refer to \(sc\(sc\ 3.2.1 and 3.2.2 of Recommendation\ G.704 for frame
structure and use of derived channel time slots.
.RT
.sp 2P
.LP
\fB3\fR     \fBLoss and recovery of frame alignment\fR
.sp 1P
.RT
.PP
The strategy for the loss and recovery of frame alignment
should be according to Rec.\ G.706, \(sc\ 3.1.
.RT
.sp 2P
.LP
\fB4\fR     \fBFault conditions\fR \fBand consequent actions\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The PCM multiplex equipment should detect the following
conditions:
.RT
.PP
4.1.1
Failure of power supply.
.PP
4.1.2
Loss of incoming signals at 6312 kbit/s.
.PP
4.1.3
Loss of frame alignment.
.PP
4.1.4
Alarm indication received from the remote PCM multiplex
equipment.
.sp 1P
.LP
4.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to the detection of a fault condition, appropriate actions should
be taken as specified in Table\ 1/G.746. The consequent actions are as
follows:
.RT
.PP
4.2.1
A service alarm indication should be generated to signify that the service
provided by the PCM multiplex is no longer available. This
indication should be forwarded to the switching and/or signalling equipment
depending upon the arrangement provided.
.bp
.sp 9p
.RT
.ce
\fBH.T. [T1.746]\fR
.ce
TABLE\ 1/G.746
.ce
\fBFault conditions and consequent actions for the PCM multiplex
.ce
equipment
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(48p) | cw(36p) sw(36p) sw(36p) sw(36p) , ^  | ^  | c | c | c | c.
Equipment part     Fault condition    Consequent actions
         {
Service alarm indication generated
 }     {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote end generated
 }     {
Transmission suppressed at the analogue outputs
 }
_
.T&
lw(36p) | lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes    Yes    Yes  (if practicable)    Optional
_
.T&
lw(36p) | lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) , ^  | l | c | c | c | c
^  | l | c | c | c | l.
Demultiplexer only     {
Loss of incoming signals at 6312 kbit/s
 }    Yes    Yes    Yes    Yes
    Loss of frame alignment    Yes    Yes    Yes    Yes     {
Alarm indication received from
the remote end
 }    Optional    Yes    Optional
.TE
.LP
\fINote\ 1\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.LP
\fINote\ 2\fR
\ \(em\ Indications of additional fault conditions, such as codec failure
and excessive bit errors, are left to the discretion of individual
Administrations.
.nr PS 9
.RT
.ad r
\fBTable 1/G.746 [T1.746], p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
4.2.2
The service alarm described in \(sc\ 4.2.1 above should be used to automatically
remove the associated circuits from service and to restore them to service
when frame alignment has been recovered.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The removal of the associated circuits described in
\(sc\ 4.2.2 above should be done in such a way that the circuits are not
needlessly removed in the case of a brief isolated loss of frame alignment
but are removed in the case of a permanent or intermittent loss of frame
alignment.
.PP
It is also important to minimize the impact of signalling errors which
may occur during periods of loss of frame alignment. These functions should
be provided in the PCM multiplex equipment or in the switching/signalling
equipment.
.RT
.PP
4.2.3
A prompt maintenance alarm indication should be generated to
signify that performance is below acceptable standards and maintenance
attention is required locally.
.sp 9p
.RT
.PP
4.2.4
An alarm indication to the remote end should be generated by
forcing bit\ \fIa\fR to the value\ 1.
.sp 9p
.RT
.PP
4.2.5
Transmission should be suppressed at the analogue outputs.
.sp 9p
.RT
.sp 1P
.LP
4.2.6
    \fIRapid indication of loss of frame alignment\fR
.sp 9p
.RT
.PP
An indication should be given to the Signalling System No.\ 6
equipment (digital version) when the PCM multiplex equipment (local end
only) detects a loss of frame alignment. The average time to detect and
give an
indication of random bits in the frame alignment signal bit positions should
not be greater than 3\ ms. This indication will serve the same function
as that provided by the data carrier failure alarm in the analogue version
(see
Recommendation\ Q.275 [1]).
.bp
.RT
.sp 2P
.LP
\fB5\fR     \fBSignalling\fR
.sp 1P
.RT
.sp 1P
.LP
5.1
    \fISignalling arrangement\fR
.sp 9p
.RT
.PP
Refer to \(sc\ 3.2.3 of Recommendation\ G.704.
.RT
.sp 1P
.LP
5.2
    \fILoss of multiframe alignment in case of channel associated\fR
\fIsignalling\fR
.sp 9p
.RT
.PP
Loss of multiframe alignment is assumed to have taken place when
loss of frame alignment occurs.
.RT
.sp 2P
.LP
\fB6\fR     \fBInterfaces\fR \v'3p'
.sp 1P
.RT
.LP
    Analogue: Refer to Recommendations G.712, G.713 and G.714.
.LP
    Digital: Refer to Recommendation G.703.
.sp 2P
.LP
    \fBReference\fR
.sp 1P
.RT
.LP
[1]
    CCITT Recommendation \fIData channel failure detection\fR , Vol.\ VI,
Rec.\ Q.275.
\v'1P'
.sp 2P
.LP
\fBRecommendation\ G.747\fR
.RT
.sp 2P
.ce 1000
\fBSECOND\ ORDER\ DIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING | fR \fBAT\
6312\ kbit/s\ AND\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.747''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.747    %'
.ce 0
.sp 1P
.ce 1000
\fBMULTIPLEXING\ THREE\ TRIBUTARIES\ AT\ 2048\ kbit/s\fR
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The digital multiplex equipment described in this Recommendation
is intended for use between networks using different digital hierarchies as
specified in Recommendations\ G.702 and\ G.802.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The bit rates of the tributary and multiplex signals should be
2048\ kbit/s \(+- | 0\ ppm and 6312\ kbit/s \(+- | 0\ ppm, respectively,
as specified in
Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table 1/G.747 gives the recommended 6312\ kbit/s multiplexing frame  structure.
.RT
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame alignment\fR \fBand consequent
action\fR
.sp 1P
.RT
.PP
Loss of frame alignment should be assumed to have taken place when four
consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
When frame alignment is assumed to be lost, the frame alignment device
should decide that such alignment has effectively been recovered when it
detects the presence of three consecutive correct frame alignment signals.
.PP
The frame alignment device, having detected the appeareance of a
single correct frame alignment signal, should begin a new search for the
frame alignment signal when it detects the absence of the frame alignment
signal in one of the two following frames.
.PP
\fINote\fR \ \(em\ As it is not strictly necessary to specify the detailed
frame alignment strategy, any suitable frame alignment strategy may be
used provided the performance achieved is at least as efficient in all
respects as that
obtained by the above frame alignment strategy.
.bp
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing and justification methods\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification are recommended.
.PP
The justification control signal should be distributed and use
the C\fI\fI\d\fIj\fR\\d\fIi\fR\u | (hybits (
\fIj\fR \ =\ 1, 2,\ 3;\ \fIi\fR \ =\ 1, 2,\ 3) (see Note\ 5 to
Table\ 1/G.747).
.PP
Positive justification should be indicated by the justification
control signal\ 111 and no justification by the signal\ 000. Majority decision
is recommended.
.PP
Table 1/G.747 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.LP
.sp 2
.ce
\fBH.T. [T1.747]\fR
.ce
TABLE\ 1/G.747
.ce
\fB6312 kbit/s multiplexing frame structure \fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
 {
Nominal tributary bit rate (kbit/s)
 }    2048
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    3
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (111010000)
 }    1 to 9
.T&
lw(144p) | cw(48p) .
Bits from tributaries    10 to 168
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Alarm indication to the remote multiplex equipment (Note 1)
 }    1
.T&
lw(144p) | cw(48p) .
Parity bit (Notes 2 and 3)    2
.T&
lw(144p) | cw(48p) .
 {
Bit reserved for future use (Note 4)
 }    3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 168
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
1 (Note 5)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 168
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
2 (Note 5)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 168
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
3 (Note 5)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for justification
 }    4 to 6
.T&
lw(144p) | cw(48p) .
Bits from tributaries    7 to 168
_
.T&
lw(144p) | cw(48p) .
Frame length    840 bits
.T&
lw(144p) | cw(48p) .
Bits per tributary in a frame    273 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    7.5 kbit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.453
.TE
.LP
\fINote\ 1\fR
\ \(em\ See \(sc\ 10.2.1.
.LP
\fINote\ 2\fR
\ \(em\ The parity bit |  |  if the number of marks in all tributary bits
including the bits in the justifiable time\(hyslots in the preceding frame is odd; the parity bit |  |  if the number of marks in all tributary bits including the bits in the justifiable time\(hyslots in the preceding frame is even.
.LP
\fINote\ 3\fR
\ \(em\ The implementation and the use of this parity bit procedure
are for further study.
.LP
\fINote\ 4\fR
\ \(em\ This bit should be set to 1 when not used.
.LP
\fINote\ 5\fR
\ \(em\ C
\fIj\fR
\fIi\fR
(
\fIj\fR
 |  | , 2, 3; \fIi\fR
 |  | , 2, 3) indicates the \fIi\fR
th justification control bit of the \fIj\fR
th tributary.
.nr PS 9
.RT
.ad r
\fBTable 1/G.747 [T1.747], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB6\fR     \fBjitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
    \fIMuldex jitter transfer characteristic\fR
.sp 9p
.RT
.PP
A 2048 kbit/s signal, modulated by sinusoidal jitter, should be
subject to a muldex jitter transfer characteristic within the gain/frequency
limits given in Figure\ 1/G.747. The equivalent binary content of the test
signal should be\ 1000.
.PP
\fINote\fR \ \(em\ In addition, the need to specify a demultiplexer tributary
jitter transfer characteristic from the 6312\ kbit/s demultiplexer input
to the 2048\ kbit/s demultiplexer output is for further study.
.RT
.LP
.rs
.sp 23P
.ad r
\fBFigure 1/G.747, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
6.2
    \fIOutput jitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.1
    \fITributary output jitter\fR
.sp 9p
.RT
.PP
With no jitter applied to the input ports of the multiplexer and
with the multiplexer directly connected to the demultiplexer, the peak\(hyto\(hypeak
jitter at the tributary output port should not exceed 0.2\ UI over a
measurement interval of one minute in the frequency range from \fIf\fR\d0\u\ to
100\ kHz (see Note\ 1).
.PP
When measured with an instrument incorporating a bandpass filter
having
a lower cutoff frequency of 18\ kHz, a roll\(hyoff of 20\ dB/decade and
an upper
limit of 100\ kHz, the peak\(hyto\(hypeak output jitter should not exceed
0.05\ UI when measured over a one minute interval (see Note\ 2).
.PP
\fINote\ 1\fR \ \(hy\ The frequency \fIf\fR\d0\ushould be as low as possible,
taking into account the limitations of measurement equipment. In any case\
\fIf\fR\d0\ushould be no greater than 10\ Hz.
.PP
\fINote\ 2\fR \ \(em\ For interfaces meeting the national high Q option,
detailed in Recommendation\ G.823, the lower cutoff frequency for the above
measurement should be 700\ Hz.
.bp
.RT
.sp 1P
.LP
6.2.2
    \fIMultiplexer output jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at the 6312 kbit/s output port should not
exceed 0.05\ UI when it is measured over a one minute interval within the
frequency range from\ \fIf\fR\d1\u\ =\ 10\ Hz to\ \fIf\fR\d4\u\ =\ 60\ kHz.
.RT
.sp 2P
.LP
6.3
    \fIInput jitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.3.1
    \fITributary input jitter\fR
.sp 9p
.RT
.PP
The 2048 kbit/s input port should be capable of accommodating
levels of input jitter up to the limits given in Rec.\ G.823.
.RT
.sp 1P
.LP
6.3.2
    \fIDemultiplexer input jitter\fR
.sp 9p
.RT
.PP
The 6312 kbit/s input port should be capable of accommodating
levels of input jitter up to the limits given in Figure\ 2/G.747.
.PP
\fINote\ 1\fR \ \(em\ Current Recommendation G.703 does not refer to the
jitter tolerated at the digital distribution frame at 6312\ kbit/s nor
at the input
port of equipment connected to this distribution frame.
.PP
\fINote\ 2\fR \ \(em\ The jitter accommodation requirement should be met when
the jittered input signal is composed of the multiplexed tributary signals
having any value of jitter allowed for the 2048\ kbit/s.
.RT
.LP
.rs
.sp 32P
.ad r
\fBFigure 2/G.747, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB7\fR     \fBDigital interfaces\fR
.sp 1P
.RT
.PP
The digital interfaces at 2048 kbit/s and 6312 kbit/s should be in accordance
with Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexing timing signal from an external source as well as from
an internal source.
.RT
.sp 2P
.LP
\fB9\fR     \fBService digits\fR
.sp 1P
.RT
.PP
Three bits per frame are available for service functions (see
Table\ 1/G.747): bit\ 1 of Set\ II is used to transmit an alarm indication
to the remote multiplex equipment when specific fault conditions are detected
in the multiplex equipment (see \(sc\ 10 below); bit\ 2 of Set\ II may
be used for a parity check; bit\ 3 of Set\ II is reserved for future use.
.RT
.LP
\fB10\fR     \fBFault conditions and consequent actions\fR
.sp 1P
.RT
.sp 2P
.LP
10.1
    \fIFault conditions\fR
.sp 1P
.RT
.PP
10.1.1
The digital multiplex equipment should detect the following fault  conditions:
.sp 9p
.RT
.LP
    1)
    failure of power supply;
.LP
    2)
    loss of an incoming 2048 kbit/s tributary signal at a
multiplexer input port;
.LP
    3)
    loss of an incoming 6312 kbit/s multiplex signal at a
demultiplexer input port;
.LP
    4)
    loss of frame alignment signal at a demultiplexer input
port;
.LP
    5)
    detection of an alarm indication received from the remote
multiplex equipment at a demultiplexer input port;
.LP
    6)
    detection of alarm indication signal (AIS) at a
demultiplexer input port.
.PP
\fINote\ 1\fR \ \(em\ The equivalent binary content of the AIS at 2048 and
6312\ kbit/s should be a continuous stream of binary\ 1s (marks) as recommended
in Recommendation\ M.20.
.PP
\fINote\ 2\fR \ \(em\ Some current 44 | 36/6312 kbit/s demultiplexers do
not issue a 6312\ kbit/s AIS. Thus no detection can take place in that
case.
.PP
\fINote\ 3\fR \ \(em\ The strategy for detecting the presence of the AIS
should be such that the AIS is detectable even in the presence of an error
ratio of
1 | (mu | 0\uD\dlF261\u3\d. However, a signal with all bits except the
frame alignment
signal in the state of\ 1 should not be mistaken as an AIS.
.RT
.PP
10.1.2
The need to monitor the degradation of the incoming 6312 kbit/s
signal for the purpose of end\(hyto\(hyend error performance monitoring of the
6132\ kbit/s digital block as well as the procedure for detecting such
degradation, are for further study.
.sp 9p
.RT
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to the detection of a fault condition, the appropriate
actions should be taken as specified in Table\ 2/G.747.
.PP
\fINote\ 1\fR \ \(em\ The concept and definition of prompt maintenance alarm
indication is given in Recommendation\ M.20.
.PP
\fINote\ 2\fR \ \(em\ When the alarm indication signal (AIS) is detected
at the input of the demultiplexer, the prompt maintenance alarm indication
associated with loss of frame alignment should be inhibited, while the
rest of the
consequent actions are in accordance with those associated in Table\ 2/G.747
with the fault condition.
.RT
.PP
10.2.1
Alarm indication to the remote multiplex equipment should be
generated by changing bit\ 1 of Set\ II (see Table\ 1/G.747) from the state\
0 to the state\ 1.
.bp
.sp 9p
.RT
.PP
10.2.2
AIS should be applied to the following as specified in
Table\ 2/G.747.
.sp 9p
.RT
.LP
    \(em
    all three 2048 kbit/s tributary outputs from the
demultiplexer;
.LP
    \(em
    6312 kbit/s output of the multiplexer;
.LP
    \(em
    the time slots of the 6312 kbit/s signal at the ouptput of
the multiplexer, corresponding to the relevant 2048\ kbit/s
tributary.
.LP
.sp 2
.ce
\fBH.T. [T2.747]\fR
.ce
TABLE\ 2/G.747
.ce
\fBFault conditions and consequent actions\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part      {
Fault condition
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplex equipment generated
 }    AIS applied     To all the tributaries    To the composite signal     {
To the relevant time slots
of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes        Yes, if practicable    Yes, if practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 6312 kbit/s
 }    Yes    Yes    Yes    Loss of frame alignment    Yes
    Yes    Yes     {
Alarm indication received from
the remote multiplex equipment
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTableau 2/G.747 [T2.747], p. 15\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 8P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.IP
\fB7.5\ Principal characteristics of higher order multiplex equipments\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ G.751\fR
.RT
.sp 2P
.ce 1000
\fBDIGITAL\ MULTIPLEX\ EQUIPMENTS\ OPERATING\ AT\ THE\ THIRD\ ORDER\ BIT\
RATE | fR \fBOF\ 34 | 68\ kbit/s\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.751''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.751    %'
.ce 0
.ce 1000
\fBAND\ THE\ FOURTH\ ORDER\ BIT\ RATE\ OF\ 139 | 64\ kbit/s\fR
.ce 0
.sp 1P
.ce 1000
\fBAND\ USING\ POSITIVE\ JUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral characteristics\fR
.sp 1P
.RT
.PP
1.1
There should be a 4th\(hyorder bit rate of 139 | 64\ kbit/s in the
digital hierarchy which is based on the 2nd\(hyorder bit rate of 8448\ kbit/s.
.sp 9p
.RT
.PP
There should be two methods of achieving the 4th\(hyorder bit
rate:
\v'3p'
.LP
     \fIMethod\ 1\fR \ \(em\ by using a 3rd\(hyorder bit rate of 34 | 68\
kbit/s in the digital hierarchy.
\v'3p'
.LP
    \fIMethod\ 2\fR \ \(em\ by directly multiplexing sixteen digital signals at
8448\ kbit/s.
.LP
    The digital signals at the bit rate of 139 | 64\ kbit/s obtained by
these two methods should be identical.
.PP
1.2
The existence of the above two methods implies that the use of
the bit rate of 34 | 68\ kbit/s should not be imposed on an Administration
that does not wish to realize the corresponding equipment.
.sp 9p
.RT
.PP
1.3
In accordance with the above two methods, the following
realizations of digital multiplex equipments using positive justification
are recommended:
\v'3p'
.sp 9p
.RT
.LP
     \fIMethod\ 1\fR \ \(em\ Realization by separate digital multiplex equipments:
one type which operates at 34 | 68\ kbit/s and multiplexes four digital
signals at 8448\ kbit/s; the other type which operates at 139 | 64\ kbit/s
and multiplexes four digital signals at 34 | 68\ kbit/s.
.LP
     The multiplexing for the 34 | 68 kbit/s digital multiplex equipment is
recommended in \(sc\ 1.4\ below, while further specification of this equipment
is given in \(sc\ 2 below.
.LP
     The multiplexing for the 139 | 64 kbit/s digital multiplex equipment
is recommended in \(sc\ 1.5\ below, while further specification of this
equipment is given in \(sc\ 3 below.
\v'3p'
.LP
    \fIMethod\ 2\fR \ \(em\ Realization by a single digital multiplex equipment
which operates at 139 | 64\ kbit/s and multiplexes sixteen digital signals at
8448\ kbit/s.
.LP
     The digital multiplexing for the 139 | 64 kbit/s bit rate should be achieved
by multiplexing, in accordance with \(sc\ 1.5 below, four digital signals
at 34 | 68\ kbit/s, each of which is obtained by multiplexing, in accordance
with \(sc\ 1.4 below, four digital signals at 8448\ kbit/s. Further specification
of this equipment is given in \(sc\ 4 below.
.sp 2P
.LP
1.4
    \fIMultiplexing four digital signals at 8448\ kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
1.4.1
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate should be 34 | 68\ kbit/s.
.PP
The tolerance on that rate should be \(+- | 0\ parts per million (ppm).
.bp
.RT
.sp 1P
.LP
1.4.2
    \fIFrame structure\fR
.sp 9p
.RT
.PP
Table\ 1/G.751 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the bunched frame alignment signal.
.ce
\fBH.T. [T1.751]\fR
.ce
TABLE\ 1/G.751
.ce
\fB34 | 68 kbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    8448
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (1111010000)
 }    1 to 10
.T&
lw(144p) | cw(48p) .
 {
Alarm indication to the remote digital multiplex equipment
 }    11
.T&
lw(144p) | cw(48p) .
Bit reserved for national use    12
.T&
lw(144p) | cw(48p) .
Bits from tributaries    13 to 384
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification service bits C\fI\fI
1 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 384
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification service bits C\fI\fI
2 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 384
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Justification service bit C\fI\fI
3 (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaire available for justification
 }    5 to 8
.T&
lw(144p) | cw(48p) .
Bits from tributaries    9 to 384
_
.T&
lw(144p) | cw(48p) .
Frame length    1536 bits
.T&
lw(144p) | cw(48p) .
Bits per tributary    378 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    22 | 75 kbit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.436
.TE
.LP
\fINote\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates the \fIn\fR
th justification
service bit of the \fIj\fR
th tributary.
.nr PS 9
.RT
.ad r
\fBTable 1/G.751 [T1.751] p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
.sp 3
1.4.3
    \fILoss and recovery of frame alignment\fR
.sp 9p
.RT
.PP
Loss of frame alignment should be assumed to have taken place when
four consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
When frame alignment is assumed to be lost, the frame alignment device
should decide that such alignment has effectively been recovered when it
detects the presence of three consecutive frame alignment signals.
.bp
.PP
The frame alignment device having detected the appearance of a single
correct frame alignment signal, should begin a new search for the frame
alignment signal when it detects the absence of the frame alignment signal
in one of the two following frames.
.PP
\fINote\fR \ \(em\ As it is not strictly necessary to specify the detailed
frame alignment strategy, any suitable frame alignment strategy may be
used
provided the performance achieved is at least as efficient in all respects
as that obtained by the above frame alignment strategy.
.RT
.sp 1P
.LP
1.4.4
    \fIMultiplexing method\fR
.sp 9p
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification is recommended. The justification control signal
should be distributed and use the C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits
(\fIn\fR \ =\ 1, 2, 3, see
Table\ 1/G.751). Positive justification should be indicated by the signal\
111, no justification by the signal\ 000. Majority decision is recommended.
.PP
Table\ 1/G.751 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.sp 1P
.LP
1.4.5
    \fIService digits\fR
.sp 9p
.RT
.PP
Two bits per frame are available for service functions. Bit\ 11 of
Set\ I is used to transmit an alarm indication to the remote multiplex
equipment when specific fault conditions are detected in the multiplex
equipment
(see \(sc\(sc\ 2.5 and\ 4.5 below). Bit\ 12 of Set\ I is reserved for national
use. On a digital path crossing the border, this bit is fixed at\ 1.
.RT
.sp 2P
.LP
1.5
    \fIMultiplexing four digital signals at 34 | 68\ kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
1.5.1
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate should be 139 | 64\ kbit/s. The tolerance on that
rate should be \(+- | 5\ parts per million (ppm).
.RT
.sp 1P
.LP
1.5.2
    \fIFrame structure\fR
.sp 9p
.RT
.PP
Table\ 2/G.751 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the bunched frame alignment signal.
.sp 1P
.LP
1.5.3
    \fILoss and recovery of frame alignment\fR
.sp 9p
.RT
.PP
Loss of frame alignment should be assumed to have taken place when four
consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
When frame alignment is assumed to be lost, the frame alignment device
should decide that such alignment has effectively been recovered when it
detects the presence of three consecutive frame alignment signals.
.PP
The frame alignment device having detected the appearance of a single
correct frame alignment signal, should begin a new search for the frame
alignment signal when it detects the absence of the frame alignment signal
in one of the two following frames.
.PP
\fINote\fR \ \(em\ As it is not strictly necessary to specify the detailed
frame alignment strategy, any suitable frame alignment strategy may be
used provided the performance achieved is at least as efficient in all
respects as that
obtained by the above frame alignment strategy.
.RT
.sp 1P
.LP
1.5.4
    \fIMultiplexing method\fR
.sp 9p
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and positive justification
is recommended. The justification control signal should be
distributed and use the C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits (\fIn\fR \
=\ 1, 2, 3, 4, 5, see
Table\ 2/G.751). Positive justification should be indicated by the signal\
11111, no justification by the signal\ 00000. Majority decision is recommended.
.PP
Table\ 2/G.751 gives the minimum justification rate per tributary and the
nominal justification ratio.
.bp
.RT
.ce
\fBH.T. [T2.751]\fR
.ce
TABLE\ 2/G.751
.ce
\fB139 | 64 kbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    34 | 68
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (111110100000)
 }    1 to 12
.T&
lw(144p) | cw(48p) .
 {
Alarm indication to the remote digital multiplex equipment
 }    13
.T&
lw(144p) | cw(48p) .
 {
Bits reserved for national use
 }    14 to 16
.T&
lw(144p) | cw(48p) .
Bits from tributaries    17 to 488
.T&
lw(144p) | cw(48p) .
    \fISets II to V\fR
.T&
lw(144p) | cw(48p) .
 {
Justification service bits C
\fIj\fR
\fIn\fR
(\fIn\fR
 |  |  to 4) (see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 488
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
Justification service bits C
\fIj\fR
\fI5\fR
(see Note)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for justification
 }    5 to 8
.T&
lw(144p) | cw(48p) .
Bits from tributaries    9 to 488
_
.T&
lw(144p) | cw(48p) .
Frame length    2928 bits
.T&
lw(144p) | cw(48p) .
Bits per tributary    723 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    47 | 63 bit/s approx.
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.419
.TE
.LP
\fINote\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates the \fIn\fR
th justification
service bit of the \fIj\fR
th tributary.
.nr PS 9
.RT
.ad r
\fBTable 2/G.751 [T2.751], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 5
.sp 1P
.LP
1.5.5
    \fIService digits\fR
.sp 9p
.RT
.PP
Four bits per frame are available for service functions. Bit\ 13 of
Set\ I is used to transmit an alarm indication to the remote multiplex
equipment when specific fault conditions are detected in the multiplex
equipment
(see \(sc\(sc\ 3.5 and 4.5\ below). Bits\ 14 to\ 16 of Set\ I are reserved
for national
use. On a digital path crossing the border, these bits are fixed at\ 1.
.RT
.sp 2P
.LP
\fB2\fR     \fBDigital multiplex equipment operating at 34 | 68\ kbit/s and
multiplexing four tributaries at 8448\ kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
    \fIMultiplexing\fR
.sp 9p
.RT
.PP
The multiplexing for the 34 | 68 kbit/s bit rate should be in
accordance with \(sc\ 1.4.
.RT
.sp 1P
.LP
2.2
    \fIDigital interfaces\fR
.sp 9p
.RT
.PP
The digital interfaces at 8448\ kbit/s and 34 | 68\ kbit/s should be in
accordance with Recommendation\ G.703.
.bp
.RT
.sp 2P
.LP
2.3
    \fIJitter\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.1
    \fIJitter transfer characteristic\fR
.sp 9p
.RT
.PP
An 8448 kbit/s signal, modulated by sinusoidal jitter, should be
subject to a muldex jitter transfer characteristic within the gain/frequency
limits given in Figure\ 1/G.751. The equivalent binary content of the test
signal should be 1000.
.RT
.sp 1P
.LP
2.3.2
    \fITributary output jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at a tributary output in the absence of input
jitter should not exceed 0.25\ UI when measured in the frequency range
up to
400\ kHz.
.PP
When measured with an instrument incorporating a bandpass filter
having a lower cutoff frequency of 3\ kHz, a rolloff of 20\ dB/decade and an
upper limit of 400\ kHz, the peak\(hyto\(hypeak output jitter should not exceed
0.05\ UI with a probability of 99.9% during a measurement period of 10\ s.
.PP
\fINote\fR \ \(em\ For interfaces meeting the national low\ Q option detailed
in Recommendation\ G.703, the lower cutoff frequency for the above measurement
should be 80\ kHz.
.RT
.LP
.rs
.sp 26P
.ad r
\fBFigure 1/G.751 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.3.3
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
In the case where the transmitting timing signal is derived from an internal
oscillator, the peak\(hyto\(hypeak jitter at the 34 | 68\ kbit/s output
should not exceed 0.05\ UI when it is measured within the frequency range
from
\fIf\fR\d1\u\ =\ 100\ Hz to \fIf\fR\d4\u\ =\ 800\ kHz.
.RT
.sp 1P
.LP
2.4
    \fITiming signal\fR
.sp 9p
.RT
.PP
If it is economically feasible, it may be desirable to be able to
derive the multiplexer timing signal from an external source as well as
from an internal source.
.bp
.RT
.sp 2P
.LP
2.5
    \fIFault conditions\fR \fI, and consequent actions\fR
.sp 1P
.RT
.sp 1P
.LP
2.5.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The digital multiplex equipment should detect the following fault
conditions:
.RT
.PP
2.5.1.1
Failure of power supply.
.sp 9p
.RT
.PP
2.5.1.2
Loss of an incoming signal at 8448\ kbit/s at the input of
the multiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ Where separate circuits are used for the digital signal
and the timing signal then loss of either or both should constitute loss
of the
incoming signal.
.PP
2.5.1.3
Loss of the incoming signal at 34 | 68\ kbit/s at the input
of the demultiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The detection of this fault condition is required only
when it does not result in an indication of loss of frame alignment.
.PP
2.5.1.4
Loss of frame alignment.
.sp 9p
.RT
.PP
2.5.1.5
Alarm indication received from the remote multiplex
equipment at the 34 | 68\ kbit/s input of the demultiplexer (see
\(sc\ 2.5.2.2 below).
.sp 9p
.RT
.sp 1P
.LP
2.5.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to detection of a fault condition, actions should be taken as specified
by Table\ 3/G.751. The consequent actions are as follows:
.RT
.PP
2.5.2.1
Prompt maintenance alarm indication generated to signify that
performance is below acceptable standards and maintenance attention is
required locally. When the Alarm Indication Signal (AIS) (see Note\ 2 under
\(sc\ 2.5.2.5)
at 34 | 68\ kbit/s is detected at the input of the demultiplexer, the
prompt maintenance alarm indication associated with loss of frame alignment
should be inhibited, while the rest of the consequent actions are in accordance
with those associated in Table\ 3/G.751 with the fault condition.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarm activated by this maintenance alarm indication is left to the discretion
of each Administration.
.PP
2.5.2.2
Alarm indication to the remote multiplex equipment generated by changing
from the state\ 0 to the state\ 1 bit\ 11 of Set\ I at the 34 | 68\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
2.5.2.3
AIS (see Notes 1 and 2 below) applied to all four
8448\ kbit/s tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
2.5.2.4
AIS (see Notes 1 and 2 below) applied to the 34 | 68 kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
2.5.2.5
AIS (see Note 2 below) applied to time slots of the
34 | 68\ kbit/s signal at the output of the multiplexer, corresponding to the
relevant 8448\ kbit/s tributary.
.sp 9p
.RT
.PP
The method of transmitting the AIS at the output port of the
multiplexer in time slots corresponding to a faulty input tributary should
be such that the status of the justification control digits is controlled
so as to ensure that the AIS is within the tolerance specified for that
tributary.
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output of the multiplexer
equipment or at the output of the demultiplexer equipment should be in
accordance with the interface specifications.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the AIS
(AIS) at 8448\ kbit/s and 34 | 68\ kbit/s is nominally a continuous stream
of\ 1s. The strategy for detecting the presence of the AIS should be such
that the AIS is detectable even in the presence of an error ratio\ 1 | (mu | 0\uD\dlF261\u3\d.
However a signal with all bits except the frame alignment signal in the
1\ state, should not be mistaken as an AIS.
.bp
.RT
.sp 1P
.LP
2.5.3
    \fITime requirements\fR
.sp 9p
.RT
.PP
The fault detection and the application of the consequent actions given
in \(sc\(sc\ 2.5.2.2 to\ 2.5.2.5, including the detection of AIS, should
be
completed within a time limit of 1\ ms.
.RT
.ce
\fBH.T. [T3.751]\fR
.ce
TABLE\ 3/G.751
.ce
\fBFault conditions and consequent actions
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part      {
Fault condition
(see \(sc\(sc\ 2.5.1 or 3.5.1)
 }     {
Consequent actions (see \(sc\(sc\ 2.5.2 or 3.5.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplex equipment generated
 }    AIS applied     To all the tributaries    To the composite signal     {
To the relevant time slots
of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes        Yes, if practicable    Yes, if practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only    Loss of incoming signal    Yes    Yes    Yes    Loss of frame alignment     Yes
    Yes    Yes     {
Alarm indication received from
the remote multiplex equipment
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTable 3/G.751 [T3.751], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 3
.sp 2P
.LP
\fB3\fR \fBDigital multiplex equipment operating at 139 | 64\ kbit/s and\fR
\fBmultiplexing four tributaries at 34 | 68\ kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
    \fIMultiplexing\fR
.sp 9p
.RT
.PP
The multiplexing for the 139 | 64 kbit/s bit rate should be in
accordance with \(sc\ 1.5 above.
.RT
.sp 1P
.LP
3.2
    \fIDigital interfaces\fR
.sp 9p
.RT
.PP
The digital interfaces at 34 | 68\ kbit/s and 139 | 64\ kbit/s should be
in accordance with Recommendation\ G.703.
.bp
.RT
.sp 2P
.LP
3.3
    \fIJitter\fR
.sp 1P
.RT
.sp 1P
.LP
3.3.1
    \fIJitter transfer characteristic\fR
.sp 9p
.RT
.PP
A 34 | 68 kbit/s signal, modulated by sinusoidal jitter, should be subject
to a muldex jitter transfer characteristic within the gain/frequency
limits given in Figure\ 2/G.751. The equivalent binary content of the test
signal should be\ 1000.
.RT
.LP
.rs
.sp 28P
.ad r
\fBFigure 2/G.751 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.3.2
    \fITributary output jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at a tributary output in the absence of
input jitter should not exceed 0.3\ UI when measured in the frequency range
up to\ 800\ kHz.
.PP
When measured with an instrument incorporating a bandpass filter
having a lower cutoff frequency of 10\ kHz, a rolloff of 20\ dB/decade and an
upper limit of 800\ kHz, the peak\(hyto\(hypeak output jitter should not exceed
0.05\ UI with a probability of 99.9% during a measurement period of 10\ s.
.RT
.sp 1P
.LP
3.3.3
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
In the case where the transmitting timing signal is derived from an internal
oscillator, the peak\(hyto\(hypeak jitter at the 139 | 64\ kbit/s output
should not exceed 0.05\ UI when it is measured within the frequency range
from \fIf\fR\d1\u\ =\ 200\ Hz to \fIf\fR\d4\u\ =\ 3500\ kHz.
.RT
.sp 1P
.LP
3.4
    \fITiming signal\fR
.sp 9p
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexer timing signal from an external source as well as from
internal source.
.bp
.RT
.sp 2P
.LP
3.5
    \fIFault conditions\fR \fIand consequent actions\fR
.sp 1P
.RT
.sp 1P
.LP
3.5.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The digital multiplex equipment should detect the following fault   conditions:
.RT
.PP
3.5.1.1
Failure of power supply.
.sp 9p
.RT
.PP
3.5.1.2
Loss of an incoming signal at 34 | 68\ kbit/s at the input
of the multiplexer.
.sp 9p
.RT
.PP
3.5.1.3
Loss of the incoming signal at 139 | 64\ kbit/s at the input
of the demultiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The detection of this fault condition is required only
when it does not result in an indication of loss of frame alignment.
.PP
3.5.1.4
Loss of frame alignment.
.sp 9p
.RT
.PP
3.5.1.5
Alarm indication received from the remote multiplex
equipment at the 139 | 64\ kbit/s input of the demultiplexer (see
\(sc\ 3.5.2.2 below).
.sp 9p
.RT
.sp 1P
.LP
3.5.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to detection of a fault condition actions should be taken as specified
by Table\ 3/G.751. The consequent actions are as follows:
.RT
.PP
3.5.2.1
Prompt maintenance alarm indication generated to signify that
performance is below acceptable standards and maintenance attention is
required locally. When the Alarm Indication Signal (AIS) (see Note\ 2 below)
at
139 | 64\ kbit/s is detected at the input to the demultiplexer, the prompt
maintenance alarm indication associated with loss of frame alignment should
be inhibited, while the rest of the consequent actions are in accordance
with
those associated in Table\ 3/G.751 with the fault condition.
.sp 9p
.RT
.PP
3.5.2.2
Alarm indication to the remote multiplex equipment generated by changing
from the state\ 0 to the state\ 1 bit\ 13 of Set\ I at the 139 | 64\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
3.5.2.3
AIS (see Notes 1 and 2 below) applied to all four
34 | 68\ kbit/s tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
3.5.2.4
AIS (see Notes 1 and 2 below) applied to the 139 | 64\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
3.5.2.5
AIS (see Note 2 below) applied to time slots of the
139 | 64\ kbit/s signal at the output of the multiplexer corresponding to the
relevant 34 | 68\ kbit/s tributary.
.sp 9p
.RT
.PP
The method of transmitting the AIS at the output port of the
multiplexer in time slots corresponding to a faulty input tributary should
be such that the status of the justification control digits is controlled
so as to ensure that the AIS is within the tolerance specified for the
tributary.
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output of the multiplexer
equipment or at the output of the demultiplexer equipment should be in
accordance with the interface specifications.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the
AIS at 34 | 68\ kbit/s and 139 | 64\ kbit/s is nominally a continuous
stream of\ 1s. The strategy for detecting the presence of the AIS should be
such that the AIS is detectable even in the presence of an error ratio
1 | (mu | 0\uD\dlF261\u3\d. However a signal, with all bits except the
frame alignment
signal in the 1\ state, should not be mistaken for an AIS.
.RT
.sp 1P
.LP
3.5.3
    \fITime requirements\fR
.sp 9p
.RT
.PP
The fault detection and the application of the consequent actions given
in \(sc\(sc\ 3.5.2.2 to 3.5.2.5, including the detection of AIS, should
be
completed within a time limit of 1\ ms.
.RT
.sp 2P
.LP
\fB4\fR     \fBDigital multiplex equipment operating at 139 | 64\ kbit/s and
multiplexing sixteen tributaries at 8448\ kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
    \fIMultiplexing\fR
.sp 9p
.RT
.PP
The multiplexing for the 139 | 64 kbit/s bit rate should be achieved by
multiplexing, in accordance with \(sc\ 1.5 above, four digital signals
at
34 | 68\ kbit/s, each of which is obtained by multiplexing, in accordance with
\(sc\ 1.4 above, four digital signals at 8448\ kbit/s.
.bp
.RT
.sp 1P
.LP
4.2
    \fIDigital interfaces\fR
.sp 9p
.RT
.PP
The digital interfaces at 8448\ kbit/s and 139 | 64\ kbit/s should be in
accordance with Recommendation\ G.703.
.RT
.sp 2P
.LP
4.3
    \fIJitter\fR
.sp 1P
.RT
.sp 1P
.LP
4.3.1
    \fIJitter transfer characteristic\fR
.sp 9p
.RT
.PP
A 8448 kbit/s signal, modulated by sinusoidal jitter, should be
subject to a muldex jitter transfer characteristic within the gain/frequency
limits given in Figure\ 3/G.751. The equivalent binary content of the test
signal should be\ 1000.
.RT
.LP
.rs
.sp 25P
.ad r
\fBFigure 3/G.751 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.3.2
    \fITributary output jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at a tributary output in the absence of
input jitter should not exceed 0.35\ UI when measured in the frequency
range up to 400\ kHz.
.PP
When measured with an instrument incorporating a bandpass filter
having a lower cutoff frequency of 3\ kHz, a rolloff of 20\ dB/decade and an
upper limit of 400\ kHz, the peak\(hyto\(hypeak output jitter should not exceed
0.05\ UI with a probability of 99.9% during a measurement period of 10\ s.
.PP
\fINote\fR \ \(em\ For interfaces meeting the national low Q option, detailed
in Recommendation\ G.703, the lower cutoff frequency for the above measurement
should be 80\ kHz.
.RT
.sp 1P
.LP
4.3.3
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
In the case where the transmitting timing signal is derived from an
internal oscillator, the peak\(hyto\(hypeak jitter at the 139 | 64\ kbit/s
output
should not exceed 0.05\ UI when it is measured within the frequency range
from \fIf\fR\d1\u\ =\ 100\ Hz to \fIf\fR\d4\u\ =\ 3500\ kHz.
.bp
.RT
.sp 1P
.LP
4.4
    \fITiming signal\fR
.sp 9p
.RT
.PP
If it is economically feasible, it may be desirable to be able to
derive the multiplexer timing signal from an external source as well as
from an internal source.
.RT
.sp 2P
.LP
4.5
    \fIFault conditions and consequent actions\fR
.sp 1P
.RT
.sp 1P
.LP
4.5.1
    \fIFault conditions\fR
.sp 9p
.RT
.PP
The digital multiplex equipment should detect the following fault
conditions:
.RT
.PP
4.5.1.1
Failure of power supply.
.sp 9p
.RT
.PP
4.5.1.2
Loss of an incoming signal at 8448\ kbit/s at the input of
the multiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ Where separate circuits are used for the digital signal
and the timing signal then loss of either or both should constitute loss
of the incoming signal.
.PP
4.5.1.3
Loss of the incoming signal at 139 | 64\ kbit/s at the input
of the demultiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The detection of this fault condition is required only
when it does not result in an indication of loss of frame alignment.
.PP
4.5.1.4
Loss of frame alignment of the signal at 139 | 64\ kbit/s at
the input of the demultiplexer.
.sp 9p
.RT
.PP
4.5.1.5
Loss of frame alignment of a signal at 34 | 68\ kbit/s
within the demultiplexer.
.sp 9p
.RT
.PP
4.5.1.6
Alarm indication received from the remote multiplex
equipment at the 139 | 64\ kbit/s input of the demultiplexer (see
\(sc\ 4.5.2.2 below).
.sp 9p
.RT
.PP
4.5.1.7
Alarm indication received from the remote multiplex
equipment on a signal at 34 | 68\ kbit/s within the demultiplexer (see
\(sc\ 4.5.2.3 below).
.sp 9p
.RT
.sp 1P
.LP
4.5.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to detection of a fault condition, actions should be taken as specified
by Table\ 4/G.751. The consequent actions are as follows:
.RT
.PP
4.5.2.1
Prompt maintenance alarm indication generated to signify that
performance is below acceptable standards and maintenance attention is
required locally. When the Alarm Indication Signal (AIS) (see Note\ 2
below) at 139 | 64\ kbit/s or 34 | 68\ kbit/s is detected by the demultiplexer,
the prompt maintenance alarm indication associated with the corresponding
loss of frame alignment should be inhibited, while the rest of the consequent
actions are in accordance with those associated in Table\ 4/G.751 with
the fault
condition.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarms activated by the maintenance alarm indication is left to the discretion
of each Administration.
.PP
4.5.2.2
Alarm indication on the 139 | 64 kbit/s signal to the remote
multiplex equipment generated by changing from the state\ 0 to the state\ 1
bit\ 13 of Set\ I at the 139 | 64\ kbit/s output of the multiplexer.
.sp 9p
.RT
.PP
4.5.2.3
Alarm indication on a 34 | 68 kbit/s signal to the remote
multiplex equipment generated by changing from the state\ 0 to the state\ 1
bit\ 11 of Set\ I on the 34 | 68\ kbit/s signal into the multiplexer.
.sp 9p
.RT
.PP
4.5.2.4
AIS (see Notes\ 1 and 2 below) applied to all sixteen
8448\ kbit/s tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
4.5.2.5
AIS (see Notes\ 1 and 2 below) applied to all four
8448\ kbit/s relevant tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
4.5.2.6
AIS (see Notes\ 1 and 2 below) applied to the 139 | 64\ kbit/s
output of the multiplexer.
.bp
.sp 9p
.RT
.PP
4.5.2.7
AIS (see Note 2 below) applied to the time slot of the
139 | 64\ kbit/s at the output of the multiplexer, corresponding to the
relevant 8448\ kbit/s tributary.
.sp 9p
.RT
.PP
The method of transmitting the AIS at the output port of the
multiplexer in time slots corresponding to a faulty input tributary, should
be such that the status of the justification control digits is controlled
so as to ensure that the AIS is within the tolerance specified for that
tributary.
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output of the multiplexer
equipment or at the output of the demultiplexer equipment should be in
accordance with the interface specifications.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the
AIS at 8448\ kbit/s, 34 | 68\ kbit/s and 139 | 64\ kbit/s is nominally a
continuous stream of\ 1s. The strategy for detecting the presence of the AIS
.PP
should be such that the AIS is detectable even in the presence of an error
ratio 1 | (mu | 0\uD\dlF261\u3\d. However a signal with all bits except
the frame
alignment signal in the 1\ state, should not be mistaken for an AIS.
.RT
.sp 1P
.LP
4.5.3
    \fITime requirements\fR
.sp 9p
.RT
.PP
The fault detection and the application of the consequent actions given
in \(sc\(sc\ 4.5.2.2 to 4.5.2.7, including the detection of AIS, should
be
completed within a time limit of 1\ ms.
.RT
.LP
.rs
.sp 37P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T4.751]\fR
.ce
TABLE\ 4/G.751
.ce
\fBFault conditions and consequent actions\fR
.ce

.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(24p) | cw(36p) | cw(24p) sw(24p) sw(24p) sw(24p) sw(24p) sw(24p) sw(24p) , ^  | ^  | c | c | c | c s s s
^  | ^  | ^  | ^  | ^  | c | c | c | l.
Equipment part      {
Fault condition (see \(sc\ 4.5.1)
 }     {
Consequent actions (see \(sc\ 4.5.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication on the 139 | 64 kbit/s signal to
the remote multiplex equipment generated
 }     {
Alarm indication
on a 34 | 68 | bit/s signal
to the remote multiplex equipment generated
 }     {
AIS applied
To all the 16 tribu\(hy taries at 8448\ kbit/s at the output
of the
demultiplexer
 }     {
To the 4 relevant tributaries at
8448 kbit/s at the output
of
the demultiplexer
 }     {
To the composite signal at 139 | 64 kbit/s
at the output
of the
multiplexer
 }     {
To the relevant time slot
of the composite signal
 }
_
.T&
lw(24p) | lw(36p) | cw(24p) | lw(24p) | lw(24p) | cw(24p) | lw(24p) | cw(24p) | lw(24p) .
Multiplexer and demultiplexer    Loss  of power supply    Yes            Yes, if practicable        Yes, if practicable
_
.T&
lw(24p) | lw(36p) | cw(24p) | lw(24p) | lw(24p) | cw(24p) | lw(24p) | cw(24p) | cw(24p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                        Yes
_
.T&
lw(24p) | lw(36p) | cw(24p) | cw(24p) | cw(24p) | lw(24p) | cw(24p) | cw(24p) | cw(24p) , ^  | l | l | c | c | c | l | l | l
^  | l | l | l | l | l | l | l | l
^  | l | l | l | l | l | l | l | l
^  | l | l | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 139 | 64\(hykbit/s
 }    Yes    Yes    Yes     {
Loss of frame alignment on the 139 | 64\ kbit/s signal
 }    Yes    Yes    Yes
     {
Alarm indication received from the remote multiplex equipment on
the 139 | 64 kbit/s signal
 }     {
Loss of frame alignment on a 34 | 68\ kbit/s signal
 }    Yes    Yes    Yes     {
Alarm indication received from the remote multiplex equipment
on a 34 | 68\(hykbit/s signal
 }
.TE
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTABLEAU 4/G.751 [T4.751], p. 22\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ G.752\fR
.RT
.sp 2P
.ce 1000
\fBCHARACTERISTICS\ OF\ DIGITAL\ MULTIPLEX\ EQUIPMENTS\ BASED\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.752''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.752    %'
.ce 0
.sp 1P
.ce 1000
\fBON\ A\ SECOND\ ORDER\ BIT\ RATE\ OF\ 6312\ kbit/s\ AND\ USING\ POSITIVE | fR
\fBJUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; amended at Geneva, 1980)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
    The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that various third\(hy and higher\(hyorder multiplex equipments exist due
to the differing characteristics of networks and signal sources in
those networks;
.PP
(b)
that, although studies will continue with the aim of
reducing the differences between various systems, the existing situation
cannot be changed in the near future;
.sp 1P
.LP
\fIrecommends the following\fR
.sp 9p
.RT
.PP
(1)
when countries using 1544 kbit/s primary multiplex equipments,
such as the PCM multiplex equipment according to Recommendation\ G.733 and
second\(hyorder multiplex using 6312\ kbit/s according to Recommendations\
G.743 and G.746, are planning digital paths requiring interconnection at
higher bit rates they should, when practical, utilize third\(hyorder bit
rates of either
32 | 64\ kbit/s or 44 | 36\ kbit/s. When countries using 32 | 64\ kbit/s
third\(hyorder multiplex equipments are planning digital paths requiring
interconnection at
higher bit rates, they should, when practical, utilize the fourth\(hyorder bit
rate of 97 | 28\ kbit/s.
.PP
For Figure\ 1/G.752 refer to Figure 1/G.702 for the basic multiplex arrangements
recommended for Administrations using 1544\ kbit/s primary
multiplex equipment. The bit rates of terrestrial systems should accommodate
multiples of 1544\ kbit/s. Whenever practical, the bit rate should also
accommodate a multiple of 6312\ kbit/s, either 32 | 64 or 44 | 36\ kbit/s, and
97 | 28\ kbit/s;
.PP
(2)
the characteristics of the third\(hyorder multiplex equipments
using positive justification is given in \(sc\ 1,\ below;
.PP
(3)
the characteristics of the fourth\(hyorder multiplex equipments
using positive justification is given in \(sc\ 2 below.
.sp 2P
.LP
\fB1\fR \fBThird\(hyorder digital multiplex equipment based on second\(hyorder
bit rate of 6312\ kbit/s and using positive justification\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
    \fIGeneral\fR
.sp 9p
.RT
.PP
The third\(hyorder digital multiplex equipment using positive
justification described below, is intended for use on digital paths and
between countries using 1544\ kbit/s and 6312\ kbit/s primary and secondary
multiplex equipments.
.PP
A bit rate of either 32 | 64\ kbit/s or 44 | 36\ kbit/s is recommended
to allow for the efficient and economical coding of wideband signals in
the
networks of Administrations using primary systems according to
Recommendations\ G.733 and G.743. For instance for a 300\ voice\(hycircuit
mastergroup (Recommendation\ G.233\ [1]) 32 | 64\ kbit/s is appropriate,
while for a 600\ voice\(hycircuit mastergroup 44 | 36\ kbit/s coding is
appropriate.
.RT
.sp 2P
.LP
1.2
     \fIThird\(hyorder digital multiplex equipment operating\fR \fIat 32 | 64\
kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
1.2.1
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate should be 32 | 64\ kbit/s. The tolerance on that rate
should be \(+- | 0\ parts per million\ (ppm).
.bp
.RT
.sp 1P
.LP
1.2.2
    \fIFrame structure\fR
.sp 9p
.RT
.PP
Table\ 1/G.752 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the frame alignment signal.
.LP
.sp 2
.ce
\fBH.T. [T1.752]\fR
.ce
TABLE\ 1/G.752
.ce
\fB 32 | 64 kbit/s multiplexing frame structure \fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    6312
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    5
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Bits for frame alignment signal (see Note\ 1)
 }    1 to 5
.T&
lw(144p) | cw(48p) .
Bits from tributaries    6 to 320
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
C
\fIj\fR
1 (
\fIj\fR
= 1 to 5) for justification control signal
(see Note\ 2)
 }    1 to 5
.T&
lw(144p) | cw(48p) .
Bits from tributaries    6 to 320
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
C
\fIj\fR
2 (
\fIj\fR
= 1 to 5) for justification control signal
(see Note\ 2)
 }    1 to 5
.T&
lw(144p) | cw(48p) .
Bits from tributaries    6 to 320
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Bits for frame alignment signal (see Note\ 3)
 }    1 to 5
.T&
lw(144p) | cw(48p) .
Bits from tributaries    6 to 320
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
C
\fIj\fR
3 (
\fIj\fR
= 1 to 5) for justification control signal
(see Note\ 2)
 }    1 to 5
.T&
lw(144p) | cw(48p) .
Bits from tributaries    6 to 320
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
Auxiliary bits H
\fIn\fR
(\fIn\fR
= 1, 2, 3, 4, 5) (see Note\ 4)
 }    1 to 5
.T&
lw(144p) | cw(48p) .
Bits from tributaries    6 to 320
_
.T&
lw(144p) | cw(48p) .
Frame length    1 | 20 bits
.T&
lw(144p) | cw(48p) .
 {
Bits per tributary (including justification)
 }    \ 378 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    16 | 00 bit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.036
.TE
.LP
\fINote\ 1\fR
\ \(em\ The frame alignment signal is a 11010 pattern.
.LP
\fINote\ 2\fR
\ \(em\ C\fI\fI
indicates the \fIn\fR
th justification
control bit of the \fIj\fR
th tributary (
\fIj\fR
= 1 to 5).
.LP
\fINote\ 3\fR
\ \(em\ The frame alignment signal is a 00101 pattern.
.LP
\fINote\ 4\fR
\ \(em\ H
5 is used for transmitting failure information from the
receive end to the transmit end.
.LP
\fINote\ 5\fR
\ \(em\ The bit available for the justification of each tributary
is the first slot of the tributary in set\ VI.
.nr PS 9
.RT
.ad r
\fBTable 1/G.752 [T1.752] p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
1.2.3
    \fILoss and recovery of frame alignment and consequent action\fR
.sp 9p
.RT
.PP
The frame alignment recovery time should not exceed 8\ ms. The
signal to be applied to the tributaries during the out\(hyof\(hyframe alignment
time should be studied.
.RT
.sp 1P
.LP
1.2.4
    \fIMultiplexing method\fR
.sp 9p
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification is recommended.
.PP
The justification control signal should be distributed and the
C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits should be used (\fIn\fR \ =\ 1, 2,
3, see Table\ 1/G.752).
.PP
Positive justification should be indicated by the signal\ 111, no
justification by the signal\ 000. Majority decision is recommended.
.PP
Table\ 1/G.752 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.sp 2P
.LP
1.2.5
    \fIJitter\fR
.sp 1P
.RT
.sp 1P
.LP
1.2.5.1
    \fISpecifications at the input ports\fR
.sp 9p
.RT
.PP
The digital signal presented at the input ports shall be as defined in
Recommendation\ G.703 modified by the transmission characteristic of the
interconnecting cable. The input ports shall be able to tolerate a digital
signal with these electrical characteristics but modified by sinusoidal
jitter up to the limits specified by the amplitude frequency relationship
in
Figure\ 2/G.752. The equivalent binary content of the signal, with jitter
modulation, applied to the inputs shall be a pseudo\(hyrandom bit sequence of
length\ 2\u1\d\u5\d\ \(em\ 1.
.PP
\fINote\fR \ \(em\ The signal with jitter modulation applied to the
demultiplexer input shall contain the bits necessary for framing and
justification in addition to information bits.
.RT
.LP
.rs
.sp 26P
.ad r
\fBFigure 2/G.752 p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
1.2.5.2
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
The jitter at the 32 | 64 kbit/s output of the multiplexer should
not exceed 0.01\ UI\ rms.
.RT
.sp 1P
.LP
1.2.5.3
     \fIDemultiplexer output jitter with no multiplexer or\fR \fIdemultiplexer
input jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at a tributary output of the demultiplexer
with no jitter at the inputs should not exceed 0.2\ UI.
.RT
.sp 1P
.LP
1.2.5.4
    \fIDemultiplexer jitter transfer characteristic\fR
.sp 9p
.RT
.PP
A 6312 kbit/s signal, modulated by sinusoidal jitter, should be
subject to a demultiplexer jitter transfer characteristic within the
gain/frequency limits given in Figure\ 3/G.752.
.RT
.LP
.rs
.sp 13P
.ad r
\fBFigure 3/G.752 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
1.2.6
    \fIDigital interface\fR
.sp 9p
.RT
.PP
The digital interfaces at 6312\ kbit/s and 32 | 64\ kbit/s should be in
accordance with Recommendation\ G.703.
.RT
.sp 1P
.LP
1.2.7
    \fITiming signal\fR
.sp 9p
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexer timing signal from an external source as well as from an
internal source.
.RT
.sp 1P
.LP
1.2.8
    \fIService digits\fR
.sp 9p
.RT
.PP
The service digits are reserved for national use.
.RT
.sp 2P
.LP
1.3
    \fIThird\(hyorder digital multiplex operating at 44 | 36\ kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.1
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate should be 44 | 36\ kbit/s. The tolerance on
that rate should be \(+- | 0\ parts per million (ppm).
.RT
.sp 1P
.LP
1.3.2
    \fIFrame structure\fR  | (see Table 2/G.752).
.sp 9p
.RT
.sp 1P
.LP
1.3.3
    \fILoss and recovery of frame and multiframe alignment and\fR
\fIconsequent action\fR
.sp 9p
.RT
.PP
The frame alignment recovery time should not exceed 2.5\ ms. The
signal to be applied to the tributaries during the out\(hyof\(hyframe alignment
time should be studied.
.PP
Once frame alignment is established, multiframe alignment should be
recovered in less than 250\ \(*ms.
.RT
.sp 1P
.LP
1.3.4
    \fIMultiplexing method\fR
.sp 9p
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification is recommended.
.bp
.PP
The justification control signal should be distributed and the
C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits should be used (\fIn\fR \ =\ 1, 2,
3, see Table\ 2/G.752).
.PP
Positive justification should be indicated by the signal\ 111, no
justification by the signal\ 000. Majority decision is recommended.
.PP
Table\ 2/G.752 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.ce
\fBH.T. [T2.752]\fR
.ce
TABLE\ 2/G.752
.ce
\fB44 | 36\(hykbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    6312
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    7
_
.T&
cw(144p) | cw(48p) .
Frame structure (see Note\ 1)    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Bit for multiframe alignment signal (M
\fIj\fR
)
(see Note\ 1)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
1st bit for frame alignment signal (F
1
1)
(see Note\ 2)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
1st bit for justification control signal
(C
\fIj\fR
1)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
2nd bit for frame alignment signal (F
0)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
2nd bit for justification control signal
(C
\fIj\fR
2)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
3rd bit for frame alignment signal (F
0)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet VII\fR
.T&
lw(144p) | cw(48p) .
 {
3rd bit for justification control signal
(C
\fIj\fR
3)
 }    1
.T&
lw(144p) | cw(48p) .
Bits from tributaries    2 to 85
.T&
lw(144p) | cw(48p) .
    \fISet VIII\fR
.T&
lw(144p) | cw(48p) .
 {
4th bit for frame alignment signal (F
1
2)
 }    1
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries (see Note\ 3)
 }    2 to 85
_
.T&
lw(144p) | cw(48p) .
Frame length    \ 680 bits
.T&
lw(144p) | cw(48p) .
Multiframe length    4760 bits
.T&
lw(144p) | cw(48p) .
 {
Bits per tributary per multiframe (including justification)
 }    \ 672 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    9398 bit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.390
.TE
.LP
\fINote\ 1\fR
\ \(em\ This frame is repeated 7 times to form a multiframe with frames
designated j |  | , 2, 3, 4, 5, 6, 7. The multiframe alignment signal is an
XXPP010 pattern where X is a bit assigned to service function, and P is the
parity bit for the preceding multiframe (i.e. from M
1 to M
7). P |  |  if
the number of marks in all tributary bits in the preceding multiframe is odd, P |  |  if the number of marks in all tributary bits in the preceding multiframe is even. Note that the two X bits are identical in any multiframe, as are the two P bits.
.LP
\fINote\ 2\fR
\ \(em\ The frame alignment signal is F
0 |  |  and
F
1
1 |  |
1
2 |  | .
.LP
\fINote\ 3\fR
\ \(em\ The bit available for the justification of tributary \fIj\fR
is the first slot of tributary \fIj\fR
following
F
1
2 in the \fIj\fR
th frame.
.LP
\fBH.T. [T3.752]\fR
    TABLE\ 3/G.752
.TS
center box ;
cw(144p) | cw(48p) .
\fB97 | 28 kbit/s multiplexing frame structure\fR
Tributary bit rate (kbit/s)    32 | 64
_
Number of tributaries    3
_
Frame structure    Bit number
_
    \fISet I\fR
Frame alignment signal (110)    1 to 3
Bits from tributaries    4 to 192
    \fISet II\fR
 {
Justification control bits C
\fIj\fR
1 (see Note\ 1)
 }    1 to 3
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bit C
\fIj\fR
2 (see Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
Frame alignment signal (001)    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
3 (see Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
Auxiliary bits H
\fIn\fR
(\fIn\fR
= 1, 2, 3) (see Note\ 2)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
_
.T&
lw(144p) | cw(48p) .
Frame length    1 | 52 bits
.T&
lw(144p) | cw(48p) .
 {
Bits per tributary per frame (including justification)
 }    \  | 78 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    84 | 33 bit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.035
.TE
.LP
\fINote\ 1\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates the \fIn\fR
th justification
bit of the \fIj\fR
th tributary (
\fIj\fR
= 1, 2, 3).
.LP
\fINote\ 2\fR
\ \(em\ This signal is H
1 H
2 H
3 pattern where H
1 is the parity bit for the preceding frame, and H
2 is a bit reserved for national use, and H
3 is a bit to transmit the failure information from the receiving end to
the transmitting end.
.LP
\fINote\ 3\fR
\ \(em\ The bit available for justification of tributary\fR
\fIj\fR
is the first slot of tributary \fIj\fR
following
H
\fIn\fR
.
.nr PS 9
.RT
.ad r
\fBTable 2/G.752 [T2.752], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
1.3.5
    \fIJitter\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.5.1
    \fISpecifications at the input ports\fR
.sp 9p
.RT
.PP
The digital signal presented at the input ports shall be as defined in
Recommendation\ G.703 modified by the transmission characteristic of the
interconnecting cable. The input ports shall be able to tolerate a digital
signal with these electrical characteristics but modified by sinusoidal
jitter up to the limits specified by the amplitude frequency relationship
in
Figure\ 4/G.752. The equivalent binary content of the signal, with jitter
modulation, applied to the inputs shall be a pseudo\(hyrandom bit sequence of
length\ 2\u1\d\u5\d\ \(em\ 1.
.PP
\fINote\fR \ \(em\ The signal with jitter modulation applied to the
demultiplexer input shall contain the bits necessary for framing and
justification in addition to information bits.
.RT
.LP
.rs
.sp 30P
.ad r
\fBFigure 4/G.752 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
1.3.5.2
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
The jitter at the 44 | 36 kbit/s multiplexer output should not
exceed 0.01\ UI\ rms.
.RT
.sp 1P
.LP
1.3.5.3
     \fIDemultiplexer output jitter with no multiplexer or\fR \fIdemultiplexer
input jitter\fR
.sp 9p
.RT
.PP
With no jitter at the input to the multiplexer and demultiplexer, the jitter
at the demultiplexer output should not exceed 1/5\ UI
peak\(hyto\(hypeak.
.bp
.RT
.sp 1P
.LP
1.3.5.4
    \fIDemultiplexer jitter transfer characteristic\fR
.sp 9p
.RT
.PP
The gain of the jitter transfer characteristic should not exceed
the limits given in Figure\ 5/G.752.
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 5/G.752 p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
1.3.6
    \fIDigital interfaces\fR
.sp 9p
.RT
.PP
The digital interfaces at 6312\ kbit/s and 44 | 36\ kbit/s should be in
accordance with Recommendation\ G.703.
.RT
.sp 1P
.LP
1.3.7
    \fITiming signal\fR
.sp 9p
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexer timing signal from an external source as well as from an
internal source.
.RT
.sp 1P
.LP
1.3.8
    \fIService digits\fR
.sp 9p
.RT
.PP
The service digits are reserved for national use.
.RT
.sp 2P
.LP
\fB2\fR \fBFourth\(hyorder multiplex equipment operating at\fR \fB97 | 28\
kbit/s\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
    \fIBit rate\fR
.sp 9p
.RT
.PP
The nominal bit rate should be 97 | 28\ kbit/s. The tolerance on that rate
should be \(+- | 0 parts per million (ppm).
.RT
.sp 1P
.LP
2.2
    \fIFrame structure\fR
.sp 9p
.RT
.PP
Table 3/G.752 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the frame alignment signal.
.bp
.sp 1P
.LP
2.3
    \fILoss and recovery of frame alignment and consequent action\fR
.sp 9p
.RT
.PP
The mean frame alignment recovery time should not exceed 1\ ms.
.PP
The signal to be applied to the tributaries during the out\(hyof\(hyframe
alignment time should be all 1s pattern.
.RT
.sp 1P
.LP
2.4
    \fIMultiplexing method\fR
.sp 9p
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification is recommended.
.PP
The justification control signal should be distributed and the
C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits should be used (\fIn\fR \ =\ 1, 2,
3, see Table\ 3/G.752).
.PP
Positive justification should be indicated by the signal 111, no
justification by the signal\ 000. Majority decision is recommended.
.PP
Table 3/G.752 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.ce
\fBH.T. [T3.752]\fR
.ce
TABLE\ 3/G.752
.ce
\fB97 | 28 kbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    32 | 64
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    3
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
Frame alignment signal (110)    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
1 (see Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bit C
\fIj\fR
2 (see Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
Frame alignment signal (001)    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
3 (see Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
Auxiliary bits H
\fIn\fR
(\fIn\fR
= 1, 2, 3) (see Note\ 2)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 192
_
.T&
lw(144p) | cw(48p) .
Frame length    1 | 52 bits
.T&
lw(144p) | cw(48p) .
 {
Bits per tributary per frame (including justification)
 }    \  | 78 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    84 | 33 bit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.035
.TE
.LP
\fINote\ 1\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates the \fIn\fR
th justification
bit of the \fIj\fR
th tributary (
\fIj\fR
= 1, 2, 3).
.LP
\fINote\ 2\fR
\ \(em\ This signal is H
1 H
2 H
3 pattern where H
1 is the parity bit for the preceding frame, and H
2 is a bit reserved for national use, and H
3 is a bit to transmit the failure information from the receiving end to
the transmitting end.
.LP
\fINote\ 3\fR
\ \(em\ The bit available for justification of tributary\fR
\fIj\fR
is the first slot of tributary \fIj\fR
following
H
\fIn\fR
.
.nr PS 9
.RT
.ad r
\fBTable 3/G.752 [T3.752], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
2.5
    \fIJitter\fR
.sp 1P
.RT
.sp 1P
.LP
2.5.1
    \fISpecifications at the input ports\fR
.sp 9p
.RT
.PP
The digital signal presented at the input ports shall be as defined in
Recommendation\ G.703 modified by the transmission characteristic of the
interconnecting cable. The input ports shall be able to tolerate a digital
signal with these electrical characteristics but modified by sinusoidal
jitter up to the limits specified by the amplitude frequency relationship
in
Figure\ 6/G.752. The equivalent binary content of the signal, with jitter
modulation, applied to the inputs shall be a pseudo\(hyrandom bit sequence of
length 2\u1\d\u5\d\ \(em\ 1.
.PP
\fINote\fR \ \(em\ The signal with jitter modulation applied to the
demultiplexer input shall contain the bits necessary for framing and
justification in addition to information bits.
.RT
.LP
.rs
.sp 30P
.ad r
\fBFigure 6/G.752, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.5.2
    \fIMultiplex signal output jitter\fR
.sp 9p
.RT
.PP
The jitter at the 97 | 28 kbit/s output of the multiplexer should
not exceed 0.01\ UI rms.
.RT
.sp 1P
.LP
2.5.3
    \fIDemultiplexer output jitter with no multiplexer or demultiplexer\fR
\fIinput jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at a tributary output of the demultiplexer
with no jitter at the inputs should not exceed\ 0.25 UI.
.bp
.RT
.sp 1P
.LP
2.5.4
    \fIDemultiplexer jitter transfer characteristic\fR
.sp 9p
.RT
.PP
A 32 | 64\ kbit/s signal, modulated by sinusoidal jitter, should be subject
to a demultiplexer jitter transfer characteristic within the
gain/frequency limits given in Figure\ 7/G.752.
.RT
.LP
.rs
.sp 13P
.ad r
\fBFigure 7/G.752, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.6
    \fIDigital interface\fR
.sp 9p
.RT
.PP
The digital interfaces at 32 | 64 kbit/s and 97 | 28\ kbit/s should be
in accordance with Recommendation\ G.703.
.RT
.sp 1P
.LP
2.7
    \fIService digits\fR
.sp 9p
.RT
.PP
The service digits are reserved for national use.
.RT
.sp 2P
.LP
    \fBReference\fR
.sp 1P
.RT
.LP
[1]
    CCITT Recommendation \fIRecommendations concerning translating\fR
\fIequipments\fR , Vol.\ III, Rec.\ G.233.
\v'1P'
.sp 2P
.LP
\fBRecommendation\ G.753\fR
.RT
.sp 2P
.ce 1000
\fBTHIRD\ ORDER\ DIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.753''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.753    %'
.ce 0
.sp 1P
.ce 1000
\fBAT\ 34 | 68\ kbit/s\ AND\ USING\ POSITIVE/ZERO/NEGATIVE\ JUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1980, further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The third order digital multiplex system with positive/zero/negative
pulse justification as given below is intended for digital connection between
countries having the same type of justification using any second order
digital systems at 8448\ kbit/s.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The nominal bit rate should be 34 | 68 kbit/s. The tolerance on that rate
should not be more than \(+- | 0 parts per million (ppm).
.bp
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table 1/G.753 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of
tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the bunched frame alignment signal.
.ce
\fBH.T. [T1.753]\fR
.ce
TABLE\ 1/G.753
.ce
\fB34 | 68\(hykbit/s multiplexing frame structure using positive/zero/negative
.ce
justification \fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    8448
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (111110100000)
 }    1 to 12
.T&
lw(144p) | cw(48p) .
 {
Bits from the secondary tributaries
 }    13 to 716
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits (C
\fIj\fR
1)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits for service functions    5 to 8
.T&
lw(144p) | cw(48p) .
 {
Justification control bits (C
\fIj\fR
2)
 }    9 to 12
.T&
lw(144p) | cw(48p) .
 {
Bits from the secondary tributaries
 }    13 to 716
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits (C
\fIj\fR
3)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
 {
Bits reserved for national use
 }    5 to 8
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for negative justification
 }    9 to 12
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for positive justification
 }    13 to 16
.T&
lw(144p) | cw(48p) .
Bits from the tributaries    17 to 716
_
.T&
lw(144p) | cw(48p) .
Frame length    2148 bits
.T&
lw(144p) | cw(48p) .
Frame duration    62.5 \(*ms
.T&
lw(144p) | cw(48p) .
Bits per tributary    528
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    16 kbit/s
.TE
.LP
\fINote\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates the \fIn\fR
th justification control
pulse of the \fIj\fR
th tributary.
.nr PS 9
.RT
.ad r
\fBTable 1/G.753 [T1.573], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame alignment and consequent actions\fR
.sp 1P
.RT
.PP
The frame alignment system should be adaptive to the error ratio in the
line link. Until frame alignment is restored the frame alignment system
should retain its position. A new search for the frame alignment signal
should be undertaken when three or more consecutive frame alignment signals
have been incorrectly received in their positions.
.PP
Frame alignment is considered to have been recovered when more than
two consecutive frame alignment signals have been correctly received in
their predicted positions.
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing method\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive\(hynegative justification with two\(hycommand control are recommended.
The justification control signal should be distributed and use C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits
(\fIn\fR \ =\ 1, 2, 3 see Table\ 1/G.753). Correction of one error in a command
is possible.
.bp
.PP
Positive justification should be indicated by the signal 111,
transmitted in each of two consecutive frames; negative justification should
be indicated by the signal\ 000, transmitted in each of two consecutive
frames, and no justification by the signal\ 111 in one frame followed by\
000 in the next
frame.
.PP
Digit time slots 9, 10, 11, 12 (Set\ III) are used for information
carrying bits (for negative justification), and digit time slots\ 13, 14,
15,\ 16 in Set\ III when it is necessary are used for no information carrying
bits (for positive justification) for the tributaries\ 1, 2, 3,\ 4.
.PP
Besides, when information from tributaries 1, 2, 3 and 4 is not
transmitted, bits\ 9, 10, 11 and 12 in Set\ III are available for transmitting
information concerning the type of justification (positive or negative) in
frames containing commands of positive justification control and intermediate
amount of jitter in frames containing commands of negative justification.
.PP
Table 1/G.753 gives maximum justification rate per
tributary.
.RT
.sp 2P
.LP
\fB6\fR     \fBJitter\fR
.sp 1P
.RT
.PP
The amount of jitter that should be tolerated at the input of the multiplexer
and the demultiplexer should be according to 3.1.1/G.823. The
amount of
jitter at the output of the multiplexer and the demultiplexer should be
studied and specified.
.RT
.sp 2P
.LP
\fB7\fR     \fBDigital interface\fR
.sp 1P
.RT
.PP
The interface at the nominal bit rate 34 | 68\ kbit/s is under
study.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
The clock should be able to be controlled by an external source.
.RT
.sp 2P
.LP
\fB9\fR     \fBService digits\fR
.sp 1P
.RT
.PP
Some spare bits per frame are available for service functions
(bits\ 5, 6 and\ 8 in Set\ II) for national and international use. Bits\
5 and\ 6 in Set\ II are available for a digital service channel (using
32\ kbit/s Adaptive
Delta Modulation) and bit\ 8 in Set\ II is available for ringing up a digital
service channel.
.RT
.sp 2P
.LP
\fB10\fR     \fBFault conditions\fR \fBand consequent actions\fR
.sp 1P
.RT
.PP
10.1
The digital multiplex equipment should detect the following
fault conditions:
.sp 9p
.RT
.PP
10.1.1
Failure of power supply.
.sp 9p
.RT
.PP
10.1.2
Loss of the incoming signal at 8448 kbit/s at the input of the  multiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ When using separate circuits for the digital signal
and the timing signal, loss of either or both of them should constitute
loss of the incoming signal.
.PP
10.1.3
Loss of the incoming signal at 34 | 68 kbit/s at the input of
the demultiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The detection of this fault condition is required only
when it does not result in an indication of loss of frame alignment.
.PP
10.1.4
Loss of frame alignment.
.sp 9p
.RT
.PP
10.1.5
Alarm indication received from the remote multiplex equipment at the 34 | 68\
kbit/s input of the demultiplexer (see \(sc\ 10.2.2 below).
.sp 9p
.RT
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
After detecting a fault condition, appropriate actions should be
taken as specified in Table\ 2/G.753. The consequent actions are as
follows:
.bp
.RT
.PP
10.2.1
Prompt maintenance alarm indication generated to signify that the performance
is below acceptable standards and maintenance attention is
required locally. When detecting the Alarm Indication Signal (AIS) at the
34 | 68\ kbit/s input of the demultiplexer the prompt maintenance alarm
indication associated with loss of frame alignment should be inhibited (see
Note\ 1 below).
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarm activated by this prompt maintenance alarm indication is left to
the
discretion of each Administration.
.PP
10.2.2
Alarm indication to the remote multiplex equipment generated by changing
from the state\ 0 to the state\ 1 bit\ 7 of Set\ II at the 34 | 68\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
10.2.3
AIS (see Note\ 2 below) applied to all four outputs of the
8448\ kbit/s tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
10.2.4
AIS (see Note\ 2 below) applied to the 34 | 68 kbit/s output of the multiplexer.
.sp 9p
.RT
.PP
10.2.5
AIS (see Note 2 below) applied to the time slots of the
34 | 68\ kbit/s signal at the multiplexer output corresponding to the relevant
8448\ kbit/s tributary.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output of the
corresponding
demultiplexer should be as specified for the tributaries. The method
of achieving this is under study.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the AIS at 8448
kbit/s and 34 | 68\ kbit/s is a continuous stream of binary\ 1s.
.RT
.ce
\fBH.T. [T2.753]\fR
.ce
TABLE\ 2/G.753
.ce
\fBFault conditions and consequent action\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part      {
Fault conditions
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplexer generated
 }    AIS applied     To all tributaries    To the composite signal      {
To the relevent time slots
of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes    Yes, if practicable    Yes, if practicable    Yes, if practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 34 | 68 kbit/s
 }    Yes    Yes    Yes    Loss of frame alignment     Yes
    Yes    Yes     {
AIS received from
the remote multiplexer
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTable 2/G.753 [T2.G.753], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ G.754\fR
.RT
.sp 2P
.ce 1000
\fBFOURTH\ ORDER\ DIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.754''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.754    %'
.ce 0
.sp 1P
.ce 1000
\fBAT\ 139 | 64\ kbit/s\ AND\ USING\ POSITIVE/ZERO/NEGATIVE\ JUSTIFICATION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1980; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The fourth order digital multiplex system with
positive/zero/negative
pulse justification as given below is intended for use on digital connection
between countries having the same type of justification using any third
order digital systems at 34 | 68\ kbit/s.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The nominal bit rate should be 139 | 64 kbit/s. The tolerance on
that rate should not be more than \(+- | 5 parts per million (ppm).
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table 1/G.754 gives:
.RT
.LP
    \(em
    the tributary bit rate and the number of
tributaries;
.LP
    \(em
    the number of bits per frame;
.LP
    \(em
    the bit numbering scheme;
.LP
    \(em
    the bit assignment;
.LP
    \(em
    the bunched frame alignment signal.
.ce
\fBH.T. [T1.754]\fR
.ce
TABLE\ 1/G.754
.ce
\fB139 | 64\(hykbit/s multiplexing frame structure using positive/zero/negative
.ce
justification \fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
Tributary bit rate (kbit/s)    34 | 68
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    4
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
Frame alignment signal    1 to 10
.T&
lw(144p) | cw(48p) .
Bits for service functions    11 to 12
.T&
lw(144p) | cw(48p) .
Bits from tributaries    13 to 544
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits (C
\fIj\fR
1)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 544
.T&
lw(144p) | cw(48p) .
    \fI\fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bit (C
\fIj\fR
2)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
Bits from tributaries    5 to 544
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bit (C
\fIj\fR
3)
 }    1 to 4
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for negative justification
 }    5 to 8
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for positive justification
 }    9 to 12
.T&
lw(144p) | cw(48p) .
Bits from tributaries    13 to 544
_
.T&
lw(144p) | cw(48p) .
Frame length    2176 bits
.T&
lw(144p) | cw(48p) .
Frame duration    15.625 \(*ms
.T&
lw(144p) | cw(48p) .
Bits per tributaries    537
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }     {
64 kbit/s
\fINote\fR
\ \(em\ C
\fIj\fR
\fIn\fR
indicates the \fIn\fR
th justification
control bit of the \fIj\fR
th tributary.
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/G.754 [T1.754], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame alignment and consequent action\fR
.sp 1P
.RT
.PP
The frame alignment system should be adaptive to the error rate in the
line link. Until frame alignment is restored the frame alignment system
should retain its position. A new search for the frame alignment signal
should be
undertaken when three and more consecutive frame alignment signals have been
incorrectly received in their position.
.PP
Frame alignment is considered to have been recovered when more than
two consecutive frame alignment signals have been correctly received in
their predicted positions.
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing method\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive\(hynegative justification with two\(hycommand control are recommended.
The justification control signal should be distributed and use C\fI\fI\d\fIj\fR\\d\fIn\fR\u\(hybits
(\fIn\fR \ =\ 1, 2, 3 see Table\ 1/G.754). Correction of one symbol error
in a command is possible.
.PP
Positive justification should be indicated by the signal 111,
transmitted in each of two consecutive frames; negative justification should
be indicated by the signal\ 000, transmitted in each of two consecutive
frames, and no justification by the signal\ 111 in one frame followed by\
000 in the next
frame.
.PP
Digit time slots 5, 6, 7, 8 (Set\ IV) are used for information carrying
bits (for negative justification), and digit time slots\ 9, 10, 11,\ 12
in
Set\ IV, when it is necessary, are used for no information carrying bits (for
positive justification) for the tributaries\ 1, 2, 3,\ 4.
.PP
Besides, when information from tributaries 1, 2, 3 and 4 is not
transmitted, bits\ 5, 6, 7 and\ 8 in Set\ IV are available for transmitting
information concerning the type of justification (positive or negative) in
frames containing commands of positive justification control and intermediate
amount of jitter in frames containing commands of negative justification.
.PP
Table 1/G.754 gives maximum justification rate per each third order
tributary.
.RT
.sp 2P
.LP
\fB6\fR     \fBJitter\fR
.sp 1P
.RT
.PP
The amount of jitter that should be accepted at the inputs of the demultiplexer
and multiplexer and should be at the output of the demultiplexer is under
study.
.RT
.sp 2P
.LP
\fB7\fR     \fBDigital interface\fR
.sp 1P
.RT
.PP
The interface at the nominal bit rates 34 | 68\ kbit/s and
139 | 64\ kbit/s is under study.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
The clock should be able to be controlled by an external
source.
.RT
.sp 2P
.LP
\fB9\fR     \fBService functions\fR
.sp 1P
.RT
.PP
Some spare bits per frame are available
for service functions (bits\ 11 and\ 12 in Set\ I) for national and international
use. Bit\ 11 in Set\ I is available for a digital service channel (using
32\ kbit/s Adaptive Delta Modulation) and bit\ 12 is available for ringing
up a digital service channel.
.RT
.sp 2P
.LP
\fB10\fR     \fBFault conditions\fR \fBand consequent actions\fR
.sp 1P
.RT
.PP
10.1
The digital multiplex equipment should detect the following
fault conditions:
.sp 9p
.RT
.PP
10.1.1
Failure of power supply.
.sp 9p
.RT
.PP
10.1.2
Loss of the incoming signal at 34 | 68\ kbit/s at the input of
the multiplexer.
.sp 9p
.RT
.PP
10.1.3
Loss of the incoming signal at 139 | 64 kbit/s at the input of the demultiplexer.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The detection of this fault condition is required only
when it does not result in an indication of loss of frame alignment.
.PP
10.1.4
Loss of frame alignment.
.sp 9p
.RT
.PP
10.1.5
Alarm indication received from the remote multiplex equipment at the 139 | 64\
kbit/s input of the demultiplexer (see \(sc\ 10.2.2 below).
.bp
.sp 9p
.RT
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
After detection of a fault condition appropriate actions should be taken
as specified in the Table\ 2/G.754 . The consequent actions are as
follows:
.RT
.PP
10.2.1
Prompt maintenance alarm indication generated to signify that the performance
is below acceptable standards and maintenance attention is
required locally. When
detecting the Alarm Indication Signal (AIS) at the 139 | 64\ kbit/s input
of the demultiplexer the prompt maintenance alarm indication associated
with loss of frame alignment should be inhibited (see Note\ 1 below).
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The location and provision of any visual and/or audible
alarm activated by this prompt maintenance alarm indication is left to
the
discretion of each Administration.
.PP
10.2.2
Alarm indication to the remote multiplex equipment generated by changing
from the state\ 0 to the state\ 1 bit\ 12 of Set\ I at the 139 | 64\ kbit/s
output of the multiplexer.
.sp 9p
.RT
.PP
10.2.3
AIS (see Note 2 below) applied to all the four outputs of the 34 | 68\
kbit/s tributary outputs from the demultiplexer.
.sp 9p
.RT
.PP
10.2.4
AIS (see Note 2 below) applied to the 139 | 64 kbit/s output of the multiplexer.
.sp 9p
.RT
.PP
10.2.5
AIS (see Note 2 below) applied to the time slots of the
139 | 64\ kbit/s
signal at the multiplexer output corresponding to the relevant 34 | 68\ kbit/s
tributary.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The bit rate of the AIS at the output of the
corresponding demultiplexer should be as specified for the tributaries.
The method of achieving this is under study.
.PP
\fINote\ 2\fR \ \(em\ The equivalent binary content of the AIS at 34 | 68
kbit/s and 139 | 64\ kbit/s is a continuous stream of binary\ 1s.
.RT
.ce
\fBH.T. [T2.754]\fR
.ce
TABLE\ 2/G.754
.ce
\fBFault conditions and consequent actions \fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part      {
Fault condition
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplexer generated
 }    AIS applied     To all tributaries     To the composite signal      {
To the relevant time slots
of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes    Yes, if practicable    Yes, if practicable    Yes, if practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 139 | 64 kbit/s
 }    Yes    Yes    Yes    Loss of frame alignment     Yes
    Yes    Yes     {
AIS received from
the remote multiplexer
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTable 2/G.754 [T2.754], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ G.755\fR
.RT
.sp 2P
.ce 1000
\fBDIGITAL\ MULTIPLEX\ EQUIPMENT\ OPERATING\ AT\ 139 | 64\ KBIT/S\fR
.EF '%    Fascicle\ III.4\ \(em\ Rec.\ G.755''
.OF '''Fascicle\ III.4\ \(em\ Rec.\ G.755    %'
.ce 0
.sp 1P
.ce 1000
\fBAND\ MULTIPLEXING\ THREE\ TRIBUTARIES\ AT\ 44 | 36\ KBIT/S\fR
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR     \fBGeneral\fR
.sp 1P
.RT
.PP
The digital multiplex equipment described in this Recommendation is intended
for use between networks using different digital hiararchies as
specified in Recommendations\ G.702 and\ G.802.
.RT
.sp 2P
.LP
\fB2\fR     \fBBit rate\fR
.sp 1P
.RT
.PP
The bit rates of the tributary and multiplex signals should be
44 | 36\ kbit/s \(+- | 0\ ppm and 139 | 64\ kbit/s \(+- | 5\ ppm, respectively,
as specified in Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB3\fR     \fBFrame structure\fR
.sp 1P
.RT
.PP
Table 1/G.755 gives the recommended 139 | 64 kbit/s multiplexing
frame structure.
.RT
.sp 2P
.LP
\fB4\fR     \fBLoss and recovery of frame alignment\fR \fB and consequent\fR
\fBaction\fR
.sp 1P
.RT
.PP
Loss of frame alignment should be assumed to have taken place when four
consecutive frame alignment signals have been incorrectly received in
their predicted positions.
.PP
When frame alignment is assumed to be lost, the frame alignment device
should decide that such alignment has effectively been recovered when it
detects the presence of three consecutive correct frame alignment signals.
.PP
The frame alignment device, having detected the appearance of a single
correct frame alignment signal, should begin a new search for the frame
alignment signal when it detects the absence of the frame alignment signal
in one of the two following frames.
.PP
\fINote\fR \ \(em\ As it is not strictly necessary to specify the detailed
frame alignment strategy, any suitable frame alignment strategy may be
used provided the performance achieved is at least as efficient in all
respects as that
obtained by the above frame alignment strategy.
.RT
.sp 2P
.LP
\fB5\fR     \fBMultiplexing and justification methods\fR
.sp 1P
.RT
.PP
Cyclic bit interleaving in the tributary numbering order and
positive justification are recommended.
.PP
The justification control signal should be distributed and use the
C\fI\fI\d\fIj\fR\\d\fIi\fR\u | (hybits (
\fIj\fR \ =\ 1, 2, 3; \fIi\fR \ =\ 1, 2, 3, 4, 5) (see Note\ 6 to
Table\ 1/G.755).
.PP
Positive justification should be indicated by the justification
control signal\ 11111 and no justification by the signal\ 00000. Majority
decision is recommended.
.PP
Table 1/G.755 gives the maximum justification rate per tributary and the
nominal justification ratio.
.RT
.sp 2P
.LP
\fB6\fR     \fBJitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
    \fIDemultiplexer triburaty jitter transfer characteristic\fR
.sp 9p
.RT
.PP
The demultiplexer 44 | 36 kbit/s tributary jitter transfer
characteristic should meet the gain/frequency limits given in Figure\ 1/G.755.
The equivalent binary content of the test signal used should result in
a
tributary output signal of\ 1000.
.bp
.RT
.ce
\fBH.T. [T1.755]\fR
.ce
TABLE\ 1/G.755
.ce
\fB139 | 64 kbit/s multiplexing frame structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(144p) | cw(48p) .
 {
Nominal tributary bit rate (kbit/s)
 }    44 | 36
_
.T&
lw(144p) | cw(48p) .
Number of tributaries    3
_
.T&
cw(144p) | cw(48p) .
Frame structure    Bit number
_
.T&
cw(144p) | cw(48p) .
    \fISet I\fR
.T&
lw(144p) | cw(48p) .
 {
Frame alignment signal (111110100000)
 }    1 to 12
.T&
lw(144p) | cw(48p) .
Bits from tributaries    13 to 159
.T&
lw(144p) | cw(48p) .
    \fISet II\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
1 (Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 159
.T&
lw(144p) | cw(48p) .
    \fISet III\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
2 (Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 159
.T&
lw(144p) | cw(48p) .
    \fISet IV\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
3 (Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
 {
Alarm indication to the remote multiplex equipment (Note\ 2)
 }    4
.T&
lw(144p) | cw(48p) .
Parity bit (Notes 3, 4 and 5)    5
.T&
lw(144p) | cw(48p) .
 {
Bits reserved for future use (Note\ 6)
 }    6 to 9
.T&
lw(144p) | cw(48p) .
Bits from tributaries    10 to 159
.T&
lw(144p) | cw(48p) .
    \fISet V\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
4 (Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
Bits from tributaries    4 to 159
.T&
lw(144p) | cw(48p) .
    \fISet VI\fR
.T&
lw(144p) | cw(48p) .
 {
Justification control bits C
\fIj\fR
5 (Note\ 1)
 }    1 to 3
.T&
lw(144p) | cw(48p) .
 {
Bits from tributaries available for justification
 }    4 to 6
.T&
lw(144p) | cw(48p) .
Bits from tributaries    7 to 159
_
.T&
lw(144p) | cw(48p) .
Frame length    954 bits
.T&
lw(144p) | cw(48p) .
Bits per tributary in a frame    307 bits
.T&
lw(144p) | cw(48p) .
 {
Maximum justification rate per tributary
 }    146 kbit/s
.T&
lw(144p) | cw(48p) .
Nominal justification ratio    0.545
.TE
.LP
\fINote\ 1\fR
\ \(em\ C
\fIj\fR
\fIi\fR
(
\fIj\fR
 |  | , 2, 3; \fIi\fR
 |  | , 2, 3, 4, 5)
indicates the \fIi\fR
th justification control bit of the \fIj\fR
th
tributary.
.LP
\fINote\ 2\fR
\ \(em\ See \(sc\ 10.2.1.
.LP
\fINote\ 3\fR
\ \(em\ The parity bit |  |  if the number of marks in all tributary bits
including the bits in the justifiable time\(hyslots in the preceding frame
is odd; the parity bit |  |  if the number of marks in all tributary bits
including the bits in the justifiable time\(hyslots in the preceding frame is
even.
.LP
\fINote\ 4\fR
\ \(em\ It is recognized that existing multiplex equipment installed prior to adoption of this Recommendation does not insert the parity bit.
.LP
\fINote\ 5\fR
\ \(em\ The implementation and the use of this parity bit procedure are for further study.
.LP
\fINote\ 6\fR
\ \(em\ These bits should be set to 1 when not used.
.nr PS 9
.RT
.ad r
\fBTable 1/G.755 [T1.755], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
\fINote\ 1\fR \ \(em\ This characteristic is usually measured between the high
speed and low speed interfaces of the demultiplexer and the measurements are
taken in unit intervals. It is then necessary to introduce a correction
factor to account for the difference in the size of unit intervals.
.PP
\fINote\ 2\fR \ \(em\ In addition, the need to specify a muldex jitter
transfer characteristic is for further study.
.PP
\fINote\ 3\fR \ \(em\ It is recognized that the existing multiplex equipment
designed prior to the adoption of this Recommendation might need tributary
test signals incorporating the 44 | 36\ kbit/s frame structure defined
in
Recommendation\ G.572.
.RT
.LP
.rs
.sp 16P
.ad r
\fBFigure 1/G.755, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
6.2
    \fIOutput jitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.1
    \fITributary output jitter\fR
.sp 9p
.RT
.PP
With no jitter applied to the input ports of the multiplexer and
with the multiplexer directly connected to the demultiplexer, the peak\(hyto\(hypeak
jitter at the tributary output port should not exceed 0.3\ UI when measured
over a one minute interval within the frequency range from \fIf\fR\d1\u\
=\ 10\ Hz to
\fIf\fR\d4\u\ =\ 400\ Hz.
.PP
When measured with an instrument incorporating a bandpass filter
having a lower cutoff frequency of \fIf\fR\d3\u\ =\ 60\ kHz, a roll\(hyoff
of 20\ dB/decade and an upper limit of \fIf\fR\d4\u\ =\ 400\ kHz, the peak\(hyto\(hypeak
output jitter should not exceed 0.05\ UI when it is measured over a one
minute interval.
.RT
.sp 1P
.LP
6.2.2
    \fIMultiplexer output jitter\fR
.sp 9p
.RT
.PP
The peak\(hyto\(hypeak jitter at the 139 | 64 kbit/s output port should
not exceed 0.05\ UI when it is measured over a one minute interval within the
frequency range from 200\ Hz to 3500\ kHz.
.RT
.sp 2P
.LP
6.3
    \fIInput jitter\fR
.sp 1P
.RT
.sp 1P
.LP
6.3.1
    \fITributary input jitter\fR
.sp 9p
.RT
.PP
The 44 | 36 kbit/s input port should be capable of accommodating
levels of input jitter up to the limits given in Figure\ 2/G.755.
.PP
\fINote\fR \ \(em\ Current Recommendation G.703 does not refer to the jitter
tolerated at the digital distribution frame at 44 | 36\ kbit/s nor at the
input port of equipment connected to this distribution frame.
.bp
.RT
.LP
.rs
.sp 27P
.ad r
\fBFigure 2/G.755, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.3.2
    \fIDemultiplexer input jitter\fR
.sp 9p
.RT
.PP
The 139 | 64 kbit/s input port should be capable of accommodating
levels of input jitter up to the limits given in Recommendation\ G.823.
.PP
\fINote\fR \ \(em\ The jitter accommodation requirement should be met when
the jittered input signal is composed of the multiplexed tributary signals
having any value of jitter allowed for the 44 | 36\ kbit/s level.
.RT
.sp 2P
.LP
\fB7\fR     \fBDigital interfaces\fR
.sp 1P
.RT
.PP
The digital interfaces at 44 | 36 kbit/s and 139 | 64 kbit/s should be
in accordance with Recommendation\ G.703.
.RT
.sp 2P
.LP
\fB8\fR     \fBTiming signal\fR
.sp 1P
.RT
.PP
If it is economically feasible, it may be desirable to be able to derive
the multiplexing timing signal from an external source as well as from
an internal source.
.RT
.sp 2P
.LP
\fB9\fR     \fBService digits\fR
.sp 1P
.RT
.PP
Six bits per frame are available for service functions (see
Table\ 1/G.755): bit\ 4 of Set\ IV is used to transmit an alarm indication
to the remote multiplex equipment when specific fault conditions are detected
in the multiplex equipment when specific fault conditions are detected
in the
multiplex equipment (see \(sc\ 10 below); bit\ 5 of Set\ IV may be used
for a parity check; bits\ 6 to\ 9 of Set\ IV are reserved for further use.
.bp
.RT
.LP
\fB10\fR     \fBFault conditions and consequent actions\fR
.sp 1P
.RT
.sp 2P
.LP
10.1
    \fIFault conditions\fR
.sp 1P
.RT
.PP
10.1.1
The digital multiplex equipment should detect the following
fault conditions:
.sp 9p
.RT
.LP
    1)
    failure of power supply;
.LP
    2)
    loss of an incoming 44 | 36 kbit/s tributary signal at a
multiplexer input port;
.LP
    3)
    loss of an incoming 139 | 64 kbit/s multiplex signal at a
demultiplexer input port;
.LP
     \fINote\fR \ \(em\ The detection of this fault condition is required
only when it does not result in an indication of loss of frame alignment.
.LP
    4)
    loss of frame alignment signal at a demultiplexer input
port;
.LP
    5)
    detection of an alarm indication received from the remote
multiplex equipment at a demultiplexer input port;
.LP
    6)
    detection of alarm indication signal (AIS) at a
demultiplexer input port.
.PP
\fINote\ 1\fR \ \(em\ The equivalent binary content of the AIS at
139 | 64\ kbit/s should be a continuous stream of binary\ 1s (marks) as
recommended in Recommendation\ M.20.
.PP
\fINote\ 2\fR \ \(em\ The strategy for detecting the presence of the AIS
should be such that the AIS is detectable even in the presence of an error
ratio of
1\ \(mu\ 10\uD\dlF261\u3\d. However, a signal with all bits except the
frame alignment
signal in the state of\ 1 should not be mistaken as an AIS.
.RT
.PP
10.1.2
The need to monitor the degradation of the incoming
139 | 64\ kbit/s signal for the purpose of end\(hyto\(hyend error performance
monitoring of the 139 | 64\ kbit/s digital block, as well as the procedure for
detecting such degradation are for further study.
.sp 9p
.RT
.sp 1P
.LP
10.2
    \fIConsequent actions\fR
.sp 9p
.RT
.PP
Further to the detection of a fault condition, the appropriate
actions should be taken as specified in Table\ 2/G.755.
.PP
\fINote\ 1\fR \ \(em\ The concept and definition of prompt maintenance alarm
indication is given in Recommendation\ M.20.
.PP
\fINote\ 2\fR \ \(em\ When the alarm indication signal (AIS) is detected
at the input of the demultiplexer, the prompt maintenance alarm indication
associated with loss of frame alignment should be inhibited, while the
rest of the
consequent actions are in accordance with those associated in Table\ 2/G.755
with the fault condition.
.RT
.PP
10.2.1
Alarm indication to the remote multiplex equipment should be
generated by changing bit\ 4 of Set\ IV (see Table\ 1/G.755) from the state\
0 to the state\ 1.
.sp 9p
.RT
.PP
10.2.2
AIS should be applied to the following as specified in
Table\ 2/G.755:
.sp 9p
.RT
.LP
    \(em
    all three 44 | 36 kbit/s tributary outputs from the
demultiplexer;
.LP
    \(em
    139 | 64 kbit/s output of the multiplexer;
.LP
    \(em
     the time slots of the 139 | 64 kbit/s signal at the output of the multiplexer,
corresponding to the relevant 44 | 36\ kbit/s tributary.
.PP
\fINote\fR \ \(em\ The equivalent binary content of the AIS at 44 | 36
kbit/s is a signal with a valid frame alignment signal, parity and justification
control bits as defined in Table\ 2/G.752, with the tributary bits being
set to a 1010 |  |  | \ sequence, starting with a binary\ 1 after each
frame alignment,
multi\(hyframe alignment and justification control bit, and with all justification
control bits being set to binary\ 0.
.LP
.rs
.sp 5P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.755]\fR
.ce
TABLE\ 2/G.755
.ce
\fBFault conditions and consequent actions\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(48p) | cw(30p) sw(30p) sw(30p) sw(30p) sw(30p) , ^  | ^  | c | c | c s s
^  | ^  | ^  | ^  | c | c | c.
Equipment part     {
Fault condition
(see \(sc\ 10.1)
 }     {
Consequent actions (see \(sc\ 10.2)
 }
         {
Prompt maintenance alarm indication generated
 }     {
Alarm indication to the remote multiplex equipment generated
 }    AIS applied     To all the tributaries    To the composite signal      {
To the relevant time slots
of the composite signal
 }
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | lw(30p) .
Multiplexer and demultiplexer    Failure  of power supply    Yes        Yes, if practicable    Yes, if practicable
_
.T&
lw(30p) | lw(48p) | cw(30p) | lw(30p) | cw(30p) | cw(30p) | cw(30p) .
Multiplexer only     {
Loss of incoming signal on a tributary
 }    Yes                Yes
_
.T&
lw(30p) | lw(48p) | cw(30p) | cw(30p) | cw(30p) | lw(30p) | cw(30p) , ^  | c | c | l | l | l | l
^  | l | l | l | l | l | l.
Demultiplexer only     {
Loss of incoming signal at 139 | 64 kbit/s
 }    Yes    Yes    Yes    Loss of frame alignment    Yes
    Yes    Yes     {
Alarm indication received from
the remote multiplex equipment
 }
.TE
.LP
\fINote\fR
\ \(em\ A \fIYes\fR
in the table signifies that a certain action should be taken as a consequence of the relevant fault condition. An \fIopen space\fR
in the table signifies that the relevant action should \fInot\fR
be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present the relevant action should be taken if, for at least one of the conditions, a \fIYes\fR
is defined in relation to this action.
.nr PS 9
.RT
.ad r
\fBTableau 2/G.755 [T2.755], p. 39\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp