In this system the S bit is used for circuit supervision in a
similar manner to its use for channel associated signalling.
.RT
.sp 1P
.LP
2.2.3
\fINon\(hystandard systems\fR
.sp 9p
.RT
.PP
In non\(hystandard transmission systems it will often be necessary to provide
a discrete signalling path for the transmission of circuit supervision
indications. Annex\ A to this Recommendation describes the arrangements
used for circuit supervision on TDMA/DSI satellite systems together with
the interfacing with the terrestrial channels.
.RT
.sp 2P
.LP
\fB3\fR \fBSignalling of circuit supervision indications\fR
.sp 1P
.RT
.PP
3.1
In integrated digital transmission systems interfacing directly with exchanges
(e.g. Recommendations\ G.734, G.744) and where systems connect to the other
Administrations, it is recommended that a standard form of circuit
supervision be used. This is detailed below for 2048\ kbit/s PCM systems and
1544\ kbit/s PCM systems.
.bp
.sp 9p
.RT
.sp 1P
.LP
3.2
\fI2048 kbit/s PCM systems\fR
.sp 9p
.RT
.PP
Signalling bits \*Qa\*U and \*Qb\*U of time slot 16 are used. Under
abnormal (alarm) conditions both\ a and\ b bits are set to\ 1. The normal
(no\(hyalarm) condition is when \*Qa\*U and \*Qb\*U bits are not both equal
to\ 1.
.RT
.sp 1P
.LP
3.3
\fI1544 kbit/s PCM systems\fR
.sp 9p
.RT
.PP
In this system the circuit supervision information is
generated:
.RT
.LP
\(em
by forcing bit 2 in every channel time slot to the value\ 0, or
.LP
\(em
by modifying the S bit as described in\ \(sc\ 3.1.3.2.2 of
Recommendation\ G.704 for the 12 frame multiframe, or
.LP
\(em
by sending a frame alignment alarm sequence
(1111111100000000) as described in\ \(sc\ 3.1.1.3 of Recommendation\ G.704
for the 24 frame multiframe
.FS
The third method proposed cannot ensure a proper end to
end supervision if a TDMA system with multidestination of multiplexes or
a CME is involved in the connection.
.FE
.
.sp 2P
.LP
\fB4\fR \fBActions in Signalling Systems Nos. 5, 6 and 7 when a
transmission alarm occurs\fR
.sp 1P
.RT
.PP
This section details the actions which should be taken on circuits using
Signalling Systems\ No.\ 5, No.\ 6 and No.\ 7 when a transmission alarm
occurs concerning the speech path. This annex is intended to be applied
to new exchange equipment only.
.PP
It is split into two broad areas dealing firstly with Signalling
System\ No.\ 5 and then with Signalling Systems No.\ 6 and No.\ 7. This
split is
required because the actions taken for inband signalling systems is slightly
different to that taken for common channel signalling systems.
.RT
.sp 1P
.LP
4.1
\fISignalling System No.\ 5\fR
.sp 9p
.RT
.PP
The action taken if a transmission alarm occurs during the states shown
below is as follows:
.RT
.sp 2P
.LP
4.1.1
\fIOutgoing circuit failure\fR
.sp 1P
.RT
.sp 1P
.LP
4.1.1.1
\fIIDLE STATE\fR
.sp 9p
.RT
.PP
Take the circuit out of service to outgoing traffic. Return to
service when transmission is restored.
.RT
.sp 1P
.LP
4.1.1.2
\fIREGISTER STATE\fR
.sp 9p
.RT
.PP
The register state is assumed to start with sending of seizure
signal and to end with sending of end of pulsing signal (ST).
.RT
.LP
\(em
Send clear forward.
.LP
\(em
Send a call unsuccessful indication on incoming circuit or
possibly carry out a repeat attempt.
.LP
\(em
If clear forward release guard sequence fails, inhibit the
repeat clear forward sequence. Resume the repeat clear forward sequence when
the transmission is restored limiting the number of simultaneous signals
to a value which will prevent overload of the transmission system.
.LP
\(em
If the clear forward release guard sequence is successful,
take the circuit out of service to outgoing traffic.
.sp 1P
.LP
4.1.1.3
\fISEIZED BUT AFTER REGISTER STATE\fR
.sp 9p
.RT
.LP
\(em
Wait for calling party to clear and send clear forward.
.LP
\(em
If answer signal has not been returned from called party,
send a call unsuccessful indication on incoming circuit.
.LP
\(em
If clear forward release guard sequence fails, inhibit the
repeat clear forward sequence. Resume the repeat clear forward sequence when
the transmission is restored limiting the number of simultaneous signals
to a value which will not overload the transmission system.
.LP
\(em
If clear forward release guard sequence is successful take
the circuit out of service to outgoing traffic.
.sp 1P
.LP
4.1.1.4
\fIBLOCKED\fR
.sp 9p
.RT
.LP
\(em
No special action required.
.bp
.sp 2P
.LP
4.1.2
\fIIncoming circuit failure\fR
.sp 1P
.RT
.sp 1P
.LP
4.1.2.1
\fIIDLE STATE\fR
.sp 9p
.RT
.LP
\(em
No special action required, respond to incoming call as
normal.
.sp 1P
.LP
4.1.2.2
\fIALL OTHER STATES\fR
.sp 9p
.RT
.LP
\(em
In answered state no special action to be taken, send all
signals as normal.
.LP
\(em
If answer signal has not been returned from called party,
start a time out device which after a certain interval clears the chain
beyond the faulty circuit.
.sp 2P
.LP
4.1.3
\fIBothway circuit\fR
.sp 1P
.RT
.sp 1P
.LP
4.1.3.1
\fIIDLE STATE\fR
.sp 9p
.RT
.LP
\(em
Take the circuit out of service to outgoing traffic, respond normally
to incoming signals.
.LP
\(em
Return to outgoing service when transmission is
restored.
.sp 1P
.LP
4.1.3.2
\fIOUTGOING REGISTER STATE\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.1.1.2.
.sp 1P
.LP
4.1.3.3
\fIOUTGOING AFTER REGISTER STATE\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.1.1.3.
.sp 1P
.LP
4.1.3.4
\fIINCOMING ANY STATE\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.1.2.
.sp 1P
.LP
4.1.3.5
\fIBLOCKED\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.1.1.4.
.sp 1P
.LP
4.2
\fISignalling System No.\ 6 or Signalling System No.\ 7\fR
.sp 9p
.RT
.PP
The action taken per speech circuit is as follows.
.RT
.sp 2P
.LP
4.2.1
\fIOutgoing circuit failure\fR
.sp 1P
.RT
.sp 1P
.LP
4.2.1.1
\fIIDLE STATE\fR
.sp 9p
.RT
.LP
\(em
Take the circuit out of service to outgoing traffic. Return to service
when the transmission is restored.
.sp 1P
.LP
4.2.1.2
\fIREGISTER STATE\fR
.sp 9p
.RT
.PP
The register state is assumed to start with sending of Initial
Address Message and to end with the receipt of an address complete
message.
.RT
.LP
\(em
Send clear forward.
.LP
\(em
Send a call unsuccessful indication on incoming circuit or
possibly carry out a repeat attempt to set up the call on another circuit.
.LP
\(em
Following receipt of release guard signal, take the circuit out of service
to outgoing traffic. Return to service when transmission is
restored.
.LP
\(em
Inhibit any repeat continuity check which may be taking
place.
.sp 1P
.LP
4.2.1.3
\fISEIZED BUT AFTER REGISTER STATE\fR
.sp 9p
.RT
.LP
\(em
If answer signal has not been received from called party,
send a call unsuccessful indication on incoming circuit.
.LP
\(em
If answer signal received, no special action required.
.LP
\(em
Take the circuit out of service when it becomes idle. Return to service
when the transmission is restored.
.bp
.sp 1P
.LP
4.2.1.4
\fIBLOCKED\fR
.sp 9p
.RT
.LP
\(em
No special action required.
.sp 2P
.LP
4.2.2
\fIIncoming circuit failure\fR
.sp 1P
.RT
.sp 1P
.LP
4.2.2.1
\fICIRCUIT IN ANY STATE\fR
.sp 9p
.RT
.LP
\(em
If answer signal has not been returned from called party,
start a time out device which after a certain interval clears the chain
beyond the faulty circuit.
.LP
\(em
If answer has been received no special action is required,
the transmission of blocking messages when end to end alarm continuity
is not provided should be for further study.
.sp 2P
.LP
4.2.3
\fIBothway circuit failure\fR
.sp 1P
.RT
.sp 1P
.LP
4.2.3.1
\fIIDLE STATE\fR
.sp 9p
.RT
.LP
\(em
Take the circuit out of service to outgoing traffic, the
transmission of blocking messages when end to end alarm continuity is not
provided should be for further study.
.LP
\(em
Return to outgoing service when transmission is
restored.
.sp 1P
.LP
4.2.3.2
\fIOUTGOING REGISTER STATE\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.2.1.2 above.
.sp 1P
.LP
4.2.3.3
\fIOUTGOING AFTER REGISTER STATE\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.2.1.3 above.
.sp 1P
.LP
4.2.3.4
\fIINCOMING CIRCUIT IN ANY STATE\fR
.sp 9p
.RT
.LP
\(em
See \(sc 4.2.2 above.
.sp 1P
.LP
4.2.3.5
\fIBLOCKED\fR
.sp 9p
.RT
.LP
\(em
No special action required.
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation Q.33)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCircuit supervision via TDMA/DSI satellite systems\fR
.sp 1P
.RT
.ce 0
.LP
A.1
\fIGeneral\fR
.sp 1P
.RT
.PP
A.1.1
When satellite systems employ Time Division Multiple Access
(TDMA) transmission techniques with Digital Speech Interpolation (DSI)
equipment at an earth station, the integrity of multiplex transmission
systems, FDM as well as PCM, used for terrestrial access to the satellite
system cannot be maintained within the satellite system. For exemple, time
slots\ 0 and\ 16 of a 2048\ kbit/s PCM system of the group pilot of a FDM
system may not be
available between earth stations for the transfer of signalling or transmission
alarm information. The provision of equivalent facilities over the satellite
section therefore needs special consideration.
.sp 9p
.RT
.PP
A.1.2
Although not necessarily a fault condition, an increase in circuit
activity on a TDMA/DSI system may lead to an overload condition, e.g.\ \*Qbit
stealing\*U in the DSI equipment. Conveyance of overload indicators to the
associated ISC may be used to initiate appropriate network management actions
to reduce or eliminate the overload conditions on groups of circuits routed
on the TDMA/DSI systems.
.PP
Implementation of this capability is at the discretion of
individual Administrations.
.bp
.PP
A.1.3
In accordance with Recommendation Q.7, specified signalling
systems considered to be suitable for international application via TDMA/DSI
satellite systems are:
.LP
\(em
System R2, provided that the satellite system is designed to
be transparent to pulsed inter\(hyregister signals;
.LP
\(em
System No. 5;
.LP
\(em
Systems Nos. 6 and 7.
.sp 1P
.LP
A.2
\fICircuit supervision\fR
.sp 9p
.RT
.PP
Possible methods of passing circuit supervision information for
these signalling systems via a TDMA/DSI satellite system are as follows:
.RT
.sp 1P
.LP
A.2.1
\fISignalling System R2\fR \v'3p'
.sp 9p
.RT
.LP
A.2.1.1\ \ In the case of System R2, only the digital version of line
signalling (Recommendations\ Q.421\(hyQ.424) is specified for use on international
digital links.
.LP
A.2.1.2\ \ A satellite
Line Signalling Channel (LSC)
is
required to convey the System\ R2 digital line signalling code. Two signalling
bits, \*Qa\*U and \*Qb\*U are required in the LSC for each System\ R2 terrestrial
circuit accessing the satellite section. Under transmission failure conditions,
bits \*Qa\*U and \*Qb\*U are set to State\ 1, so that the line signalling
protocols of digital\ R2 will eventually block the circuit.
.PP
Appendix I shows a typical format and organization of the LSC for System\
R2 line signalling.
.LP
A.2.1.3\ \ Fault conditions detected at the earth station and the
consequent actions to be taken are given: in Tables\ A\(hy1/Q.33 and A\(hy2/Q.33
when terrestrial access is via a 2048 kbit/s PCM system or via an FDM system
with
signalling conversion employed at the earth station, respectively.
.PP
The application of actions given in these tables enables
appropriate end\(hyto\(hyend supervision to be provided on a per\(hycircuit
basis.
.sp 1P
.LP
A.2.2
\fISignalling System No. 5\fR \v'3p'
.sp 9p
.RT
.LP
A.2.2.1\ \ It should be noted that on circuits employing System No.\ 5
signalling, some administrations utilize a repeat forward clear procedure
as a means of achieving clear down under failure conditions. This procedure,
which may involve periodic sending of forward clear signals synchronously
on a number of circuits, can result in severe periodic overloading of DSI
channels. In
order to avoid this possible overloading of DSI channels it is preferable to
limit the number of simultaneous forward clear signals on the circuits
involved.
.LP
A.2.2.2\ \ In order to convey circuit supervision information via the
satellite system, it will be necessary to provide a satellite signalling
channel.
.PP
The preferred method of conveying circuit supervision information by use
of a satellite digital non\(hyinterpolated (DNI) channel is
described in\ \(sc\ A.2.2.3.
.PP
If an LSC, as provided for in System R2, is available, then a second method
of passing circuit supervision information is as described
in\ \(sc\ A.2.2.4.
.RT
.sp 1P
.LP
A.2.2.3\ \ \fIUse of a\fR
\fIDNI supervision channel\fR
.sp 9p
.RT
.PP
When a DNI channel is utilized for circuit supervision purposes,
detection by an earth station of circuit failures on its terrestrial sector
will result in the setting of bits in the DNI channel to \*Q1\*U, in accordance
with the information contained in Appendix\ II.
.PP
Thus, if the failed circuits are digital, the detection of failure
conditions, such as loss of frame alignment, described in Table\ A\(hy3/Q.33
will result in the setting to \*Q1\*U of bits in the DNI channel associated
with the
affected circuits.
.PP
When the affected circuits are analogue, the failure will be detected at
the earth station, e.g. by the loss of pilot, or if appropriate, by receipt
of a pulsed bakward pilot. Fault conditions and consequent actions when
analogue access links are employed are given in Table\ A\(hy4/Q.33.
.PP
The alarm information passed over the DNI channel can be forwarded by the
receiving earth station to its associated ISC as described in
Recommendation\ Q.33.
.PP
An Administration may utilize the alarm information at its ISC to
block or busy affected circuits, or, for example, to inhibit the sending of
repeat forward clear signals.
.PP
Appendix II shows the format and organization of the DNI supervisory channel.
.bp
.RT
.sp 1P
.LP
A.2.2.4\ \ \fIUse of System R2 LSC\fR
.sp 9p
.RT
.PP
In this case the \*Qa\*U and \*Qb\*U signalling bits in the LSC
corresponding to the Terrestrial Channels (TCs) for which supervision is
applied shall assume the following meaning:
.PP
Under normal conditions:
.RT
.LP
b = 0 indicates that the relevant TC is in a normal condition.
The b\ =\ 0 state may be established either within the TDMA
terminal or at the ISC.
.PP
The \*Qa\*U signalling bit contained in the same slot shall be set, as
convenient, either to zero or\ \*Q1\*U.
.PP
Under abnormal conditions:
.RT
.LP
a = b = 1 indicates that the relevant TC is in an abnormal
condition.
.PP
Thus, for effective application, the failure of a distant
terrestrial transmission system (FDM or PCM) in either direction between an
earth station and its associated ISC should result in the sending of a\
=\ b\ =\ 1 for each affected circuit backward over the satellite section.
The alarm
information passed via the LSC is transferred from the receiving earth
station to its associated ISC as follows:
.LP
\(em
when digital access circuits are provided, bits a and b, in
Time Slot\ 16 corresponding to the faulty circuits, are set
to\ \*Q1\*U;
.LP
\(em
when analogue access circuits are employed receipt by the
earth station of bits\ a\ =\ b\ =\ 1 for\ 6 or more circuits in an
analogue group should result in the removal of the group pilot
towards the ISC.
.PP
This method of using two signalling bits to convey circuit
supervision information for System\ No.\ 5 circuits is inefficient in the
utilization of satellite channel capacity. However, Administrations may need
to take into account the possible advantages of such utilization, for example,
a common terrestrial interface module for both System\ R2 and System\ No.\
5
circuits may be employed at the earth station.
.PP
Appendix I shows the format and organization of the LSC for System\ R2
line signalling. Where appropriate to such use of circuits employing
System\ No.\ 5 signalling, the fault conditions and consequent actions
given in Tables\ A\(hy1/Q.33 and A\(hy2/Q.33 also apply.
.RT
.sp 1P
.LP
A.2.3
\fISignalling System No. 6 and No. 7\fR \v'3p'
.sp 9p
.RT
.LP
A.2.3.1\ \ These signalling systems employ a common signalling channel
which may be conveyed via the satellite system (for example, via a 64\ kbit/s
signalling channel) or via a terrestrial transmission path.
.LP
A.2.3.2\ \ The provision of transmission alarm information for circuit
supervision purposes is necessary because:
.LP
a)
Although a speech path continuity check, where used, will
remove faulty circuits from service, a faster method is required if
severe operational problems at the ISC are to be avoided when
a large number of circuits are affected by a transmission
system failure.
.LP
b)
In the case of circuits employing System No.\ 7, end\(hyto\(hyend circuit
supervision is required in accordance with
Recommendation\ Q.724.
.LP
c)
It is not mandatory for an ISC recognizing a transmission
system failure to send a blocking signal for each affected circuit.
.LP
A.2.3.3\ \ If the common signalling channel and associated circuits are
routed via the same satellite system, methods of conveying circuit supervision
information are identical to those described for System No.\ 5. This will
require a DNI satellite channel to carry circuit supervision information in
addition to the common signalling channel. Digital terrestrial access systems
will also require a time slot for circuit supervision purposes besides
that
required for common channel signalling.
.LP
A.2.3.4\ \ Methods of utilizing the common signalling channel in lieu of
the DNI channel for the purpose of conveying information on the status
of the transmission path of the speech circuits require further study.
.LP
A.2.3.5\ \ Fault conditions and consequent actions to be taken at earth
stations when system No.\ 6 or No.\ 7 is employed, via digital and analogue
access links, are given in Tables\ A\(hy3/Q.33 and\ A\(hy4/Q.33, respectively.
.bp
.ce
\fBH.T. [1T1.33]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(342p) .
TABLE\ A\(hy1/Q.33
.T&
cw(342p) .
{
\fBFault conditions and consequent actions at earth stations\fR
\fBwith 2048 kbit/s digital access links for System R2 circuits\fR
}
.TE
.TS
cw(72p) | cw(27p) sw(21p) sw(21p) sw(21p) | lw(27p) | lw(21p) sw(21p) sw(21p) sw(27p) sw(21p) sw(21p) sw(21p) , ^ | c | c | l | l ^ | | l | l | l | l | l | l | l.
{
Digital earth station
equipment
(digital access links)
Fault conditions
} {
Terrestrial link to own CT
Remote backward alarm indication
(bit 3, TS 0, even frames)
Backward alarm indication
(bit 6, TS 16, frame 0)
a = b = 1
in TS 16 for all circuits concerned
AIS in non\(hyinterp\(hy
olated
channels
}
Prompt maintenance alarm {
Satellite link
Action to prevent overlap of bursts in a TDMA frame
Backward alarm indication concerning data unique word
AIS in non\(hy
interpolated channels
a = b = 1
in satellite signalling channel for circuits
concerned
Block switched circuits concerned
Backward alarm indication concerning satellite
signalling channel
}
_
.T&
lw(12p) | lw(60p) | cw(27p) | cw(21p) | cw(21p) | cw(21p) | cw(27p) | lw(21p) | cw(21p) | cw(21p) | cw(27p) | lw(21p) | cw(21p) | lw(21p) , ^ | c | c | c | c | c | 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 | l | l | l
^ | l | l | l | l | l | l | l | l | l | l | l | l | l.
{
Loss of frame alignment, BER exceeded or loss of incoming signal
} Yes Yes Note 1 Yes Yes Yes Loss of multiframe alignment Yes Yes Note 1 Yes {
Alarm indication from CT
(bit 3 TS\ 0 even frame,
bit 6
TS 16 frame 0)
} Yes {
Power supply failure \(em TDMA/DSI
}
Yes if possible Yes Yes if possible Yes if possible Yes if possible {
Power supply failure \(em satellite signalling equipment
cw(72p) | cw(27p) sw(21p) sw(21p) sw(21p) | lw(27p) | lw(21p) sw(21p) sw(21p) sw(27p) sw(21p) sw(21p) sw(21p) , ^ | c | c | l | l ^ | | l | l | l | l | l | l | l.
{
Digital earth station
equipment
(digital access links)
Fault conditions
} {
Terrestrial link to own CT
Remote backward alarm indication
(bit 3, TS\ 0,
even frames)
Backward alarm indication
(bit 6, TS 16, frame 0)
a = b = 1
in TS 16 for all circuits concerned
AIS in non\(hyinterp\(hy
olated
channels
}
Prompt maintenance alarm {
Satellite link
Action to prevent overlap of bursts in a TDMA frame
lw(12p) | lw(60p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | lw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) , ^ | c | l | c | c | c | l | l | l | l | l | l
^ | l | l | l | l | l | l | l | l | l | l | l.
{
Loss of forward signal (Group pilot failure)
} Yes Yes Yes Note 4 Yes {
Power supply failure from trans. equip.
} Yes if possible Yes Yes if possible Note 4
Yes if possible {
Failure of line signal converter
} Yes Yes Note 5
_
.T&
lw(12p) | lw(60p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) | lw(30p) | lw(24p) , ^ | c ^ | | l | l | l | l | l | l | l | l | l.
{
Power supply failure \(em TDMA/DSI
} {
Power supply failure \(em satellite signalling equipment
} Yes if possible Yes Yes if possible Yes if possible Yes if possible Yes if possible Yes Yes if possible
Power supply failure \(em satellite signalling equipment
} Yes if possible Yes Yes if possible
.TE
.LP
\fINote\ 1\fR
\ \(em\ The \*Qrelevant blocking signal\*U is that signal which the
Recommendation for analogue\ R.2 line signalling calls for in the event of
interruption control or it may be the defined blocking condition resulting
from busying equipment (Orange Book, Recommendation\ Q.416 and\ Q.424).
.LP
\fINote\ 2\fR
\ \(em\ Prompt maintenance alarm shall be inhibited if the backward alarm is received from only one origin if the interface concerned is working to more
than one destination. It is not inhibited when working to a single
destination.
.LP
\fINote\ 3\fR
\ \(em\ If prompt maintenance alarm according to Note\ 2 is not inhibited.
.LP
\fINote\ 4\fR
\ \(em\ In this case the line signalling converter shall apply this
condition. It is assumed that power supply failure on FDM transmission
equipment will result in a group pilot failure.
.LP
\fINote\ 5\fR
\ \(em\ The line signalling converter should comply with the principles
described in Recommendation\ Q.422.
.LP
\fINote\ 6\fR
\ \(em\ A relevant blocking signal will be generated by the converter in the analogue part.
Backward alarm indication concerning data unique word
AIS in non\(hy
interpolated channels
Indication of fault in affected channels via circuit
supervision channel
Block switched circuits concerned
}
_
.T&
lw(12p) | cw(66p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | lw(24p) | cw(24p) | cw(24p) | cw(24p) | lw(24p) | cw(24p) | lw(24p) , ^ | c | c | c | c | c | 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.
{
Loss of frame alignment. BER exceeded or loss of incoming
signal
} Yes Note 4 Yes Note 1 Yes Yes Yes Loss of multiframe alignment Yes Yes Note 1 Yes Alarm indication from CT Yes {
Power supply failure \(em TDMA/DSI
}
Yes if possible Yes Yes if possible Yes if possible Yes if possible {
Power supply failure \(em service supervision signalling equipment
Indication of remote end transmission failure via circuit supervision
channel
} Yes
.TE
.LP
\fINote\ 1\fR
\ \(em\ Prompt maintenance alarm is inhibited if AIS is present.
.LP
\fINote\ 2\fR
\ \(em\ Prompt maintenance alarm shall be inhibited if the backward alarm is received from only one origin. If the interface concerned is working to more
than one destination. It is not inhibited when working to a single
destination.
.LP
\fINote\ 3\fR
\ \(em\ If prompt maintenance alarm according to Note 2 is not
inhibited.
.LP
\fINote\ 4\fR
\ \(em\ For a 2048\ kbit/s digital access, bit\ 3 (TS\ 0, even frames)
could be used for this indication. For a 1544\ kbit/s digital access,
fault indication as described in G.733, \(sc\ 4.2.4 could be used for
Power supply failure \(em service supervision signalling equipment
} Yes Yes Yes if possible {
Indication of remote end transmission failure via circuit supervision
channel
} Yes Note 4
.TE
.LP
\fINote\ 1\fR
\ \(em\ Prompt maintenance alarm shall be inhibited if the backward alarm is received from only one origin if the interface concerned is working to more
than one destination. It is not inhibited when working to a single
destination.
.LP
\fINote\ 2\fR
\ \(em\ If prompt maintenance alarm according to Note 1 is not inhibited.
.LP
\fINote\ 3\fR
\ \(em\ Apart from the requirements concerning the loss of group or
supergroup pilots and indication of remote and transmission failure, all other fault conditions and subsequent actions are optional.
.LP
\fINote\ 4\fR
\ \(em\ An Administration's decision to remove group or supergroup pilot is dependent on the number of failed circuits in the group or supergroup.