Number Designation Point\(hyto\(hypoint Multipoint
_
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
102\fB/1\fR T{
Signal ground or common return
T} X X X
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
103\fB/1\fR Transmitted data X X X
_
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
104\fB/1\fR Received data X X X
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
105\fB/1\fR Request to send \(em X (Note 2) X
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
106\fB/1\fR Ready for sending X X X
_
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
107\fB/1\fR Data set ready X X X
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
108/1 Connect data set to line X (Note 3) X X
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
108/2 Data terminal ready X (Note 3) X (Note 4) \(em
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
109\fB/1\fR T{
Data channel received line signal detector
T} X X X
_
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
125\fB/1\fR Calling indicator X \(em \(em
.T&
cw(24p) | lw(90p) | cw(54p) | cw(30p) | cw(30p) .
126\fB/1\fR Select transmit frequency \(em \(em X
.TE
.LP
\fINote\ 1\fR
\ \(em\ All essential interchange circuits and any others which are provided shall comply with the functional and operational requirements of
Recommandation\ V.24. All interchange circuits indicated by\ X shall be properly terminated in the data terminal equipment and in the data circuit\(hyterminating equipment in accordance with the appropriate Recommendation for electrical
characteristics (see\ \(sc\ 9).
.LP
\fINote\ 2\fR
\ \(em\ Circuit 105 is not required when alternate voice/data service is
used on non\(hyswitched leased point\(hyto\(hypoint circuits.
.LP
\fINote\ 3\fR
\ \(em\ The circuit shall be capable of operation as circuit 108/1 \(em
\fIconnect dat set to line\fR
\|or circuit 108/2 \(em
\fIdata terminal ready\fR
depending ont its use.
.LP
\fINote\ 4\fR
\ \(em\ In the leased point\(hyto\(hypoint case, where alternate voice/data
service is to be provided, circuit\ 108/2 may be used optionally.
.nr PS 9
.RT
.ad r
\fBTableau 1/V.21 [T1.21] p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
8.2
\fIResponse times of circuits\ 106 and 109\fR
.sp 1P
.RT
.sp 2P
.LP
8.2.1
\fIDefinitions\fR
.sp 1P
.RT
.PP
8.2.1.1
Circuit 109 response times are the times that elapse between
the connection or removal of a tone to or from the modem receive line terminals
and the appearance of the corresponding ON or OFF condition on circuit\
109.
.sp 9p
.RT
.PP
The test tone should have a frequency corresponding to the
characteristic frequency of binary\ 1 and be derived from a source with an
impedance equal to the nominal input impedance of the modem under
test.
.bp
.PP
The level of the test tone should fall into the level range
between 1\ dB above the actual threshold of the received line signal detector
and the maximum admissible level of the received signal. At all levels
within this range the measured response times shall be within the specified
limits.
.RT
.PP
8.2.1.2
Circuit\ 106 response times are the times from the connection of an ON
or OFF condition on:
.sp 9p
.RT
.LP
\(em
circuit\ 105 (where it is provided) to the appearance of
the corresponding OFF or ON condition on circuit\ 106;
.LP
\(em
circuit\ 109 (where circuit\ 105 is not provided) to the
appearance of the corresponding ON or OFF condition on circuit\ 106.
.sp 1P
.LP
8.2.2
\fIResponse times\fR
.sp 9p
.RT
.ce
\fBH.T. [T2.21]\fR
.ce
TABLE\ 2/V.21
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(72p) | lw(78p) | lw(78p) .
\fICircuit 106\fR
.T&
lw(72p) | lw(78p) | lw(78p) .
\ \ OFF to ON 20\(hy50 ms (see Note 1) 400\(hy1000 ms (see Note 2)
.T&
lw(72p) | cw(156p) .
\ \ ON to OFF \(= 2 ms
_
.T&
lw(72p) | lw(78p) | lw(78p) .
\fICircuit 109\fR
.T&
lw(72p) | lw(78p) | lw(78p) .
\ \ OFF to ON \(= 20 ms (see Note 1) 300\(hy700 ms (see Note 2)
.T&
lw(72p) | cw(156p) .
\ \ ON to OFF 20\(hy80 ms
.TE
.LP
\fINote\ 1\fR
\ \(em\ These times are used on leased point\(hyto\(hypoint networks without
alternate voice data facilities and on leased multipoint facilities.
.LP
\fINote\ 2\fR
\ \(em\ These times are used in the general switched network service and on leased point\(hyto\(hypoint circuits with alternate voice data.
.nr PS 9
.RT
.ad r
\fBTableau 2/V.21 [T2.21], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
8.3
\fIThreshold of data channel received line signal detector\fR
.sp 9p
.RT
.PP
Level of received line signal at received line signal terminals of modem
for all types of connection, i.e. general switched telephone network or
non\(hyswitched leased telephone circuit:
.RT
.LP
greater\ than\ \(em43\ dBm\ \ \ \ circuit 109 ON
.LP
less\ than
\ \(em48\ dBm\ \ \ \ circuit 109 OFF
.PP
The condition of circuit\ 109 for levels between \(em43\ dBm and
\(em48\ dBm is not specified except that the signal detector shall exhibit a
hysteresis action such that the level at which the OFF to ON transition
occurs shall be at least 2\ dB greater than for the ON to OFF transition.
.PP
Where transmission conditions are known on switched or leased
circuits, Administrations should be permitted at the time of modem installation
to change these response levels of the received line signal detector to
less
sensitive values (e.g. \(em33\ dBm and \(em38\ dBm respectively).
.RT
.sp 1P
.LP
8.4
\fIFault condition of interchange circuits\fR
.sp 9p
.RT
.PP
See Recommendation\ V.28, \(sc\ 7 for association of the receiver
failure detection types).
.RT
.PP
8.4.1
The DTE should interpret a fault condition on circuit 107
as an OFF condition using failure detection type\ 1.
.sp 9p
.RT
.PP
8.4.2
The DCE should interpret a fault condition on circuits 105
and\ 108 as an OFF condition using failure detection type\ 1.
.PP
8.4.3
All other circuits not referred to above may use failure
detection type\ 0 or\ 1.
.bp
.sp 2P
.LP
\fB9\fR \fBElectrical characteristics of interchange
circuits\fR
.sp 1P
.RT
.PP
Use of electrical characteristics conforming to
Recommendation\ V.28 is recommended together with the
connector and pin
assignment plan
specified by ISO\ 2110.
.PP
\fINote\fR \ \(em\ Manufacturers may wish to note that the long\(hyterm
objective is to replace electrical characteristics specified in
Recommendation\ V.28, and that Study Group\ XVII has agreed that the work
shall proceed to develop a more efficient, all\(hybalanced, interface for
the V\(hySeries application which minimizes the number of interchange circuits.
.RT
.PP
\fB10\fR
The following information is provided to assist equipment
manufacturers:
.sp 9p
.RT
.LP
\fB
a)
The nominal range of attenuations in
subscriber\(hyto\(hysubscriber connections is from 5 to 30\ dB at the
reference frequency (800 or 1000\ Hz), assuming up to 35\ dB
attenuation at the frequency 1750\ Hz.
.LP
b)
The data modem should have no adjustment for send level
or receive sensitivity under the control of the operator.
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIEcho suppressors\fR , Vol. III, Rec.\ G.164.
\fI(Geneva, 1980; amended at Malaga\(hyTorremolinos, 1984;\fR \fIand at
Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBIntroduction\fR
.sp 1P
.RT
.PP
1.1
This modem is intended for use on connections on General
Switched Telephone Networks (GSTNs), and on point\(hyto\(hypoint circuits when
suitably conditioned.
.sp 9p
.RT
.PP
The principal characteristics of this modem are as
follows:
.LP
a)
duplex operation on 2\(hywire GSTN and point\(hyto\(hypoint leased
circuits,
.LP
b)
channel separation by frequency division,
.LP
c)
differential phase shift modulation for each channel with
synchronous line transmission at 600 bauds (nominal),
.LP
d)
inclusion of a scrambler,
.LP
e)
inclusion of test facilities.
.PP
1.2
Recognizing the wide range of application, this Recommendation
provides for three alternative configurations. The choice of alternative
is a matter for the Administration concerned. The facilities given by the
alternatives are:
\v'2p'
.sp 9p
.RT
.LP
\fIAlternative A\fR
.LP
1200\ bit/s synchronous
.LP
\ 600\ bit/s synchronous (optional)
\v'2p'
.LP
\fIAlternative B\fR
.LP
1200\ bit/s\ synchronous
\(*H
.LP
\(*K\ as in Alternative\ A
.LP
\ 600\ bit/s\ synchronous\ (optional)
\(rb
.LP
1200\ bit/s\ start\(hystop
.LP
\ 600\ bit/s start\(hystop (optional)
\v'2p'
.LP
\fIAlternative C\fR
.LP
1200\ bit/s\ synchronous
.LP
\ 600\ bit/s\ synchronous\ (optional)
.LP
\ as in Alternative\ B
.LP
1200\ bit/s\ start\(hystop
.LP
\ 600\ bit/s\ start\(hystop\ (optional)
.LP
An asynchronous mode having capability of handling 1200 bit/s
start\(hystop and anisochronous data at up to 300\ bit/s.
.bp
.PP
The selection of the asynchronous mode is made during the
handshaking sequence (see \(sc\ 6). This gives compatibility between Alternative\
B and Alternative\ C.
.PP
\fINote\fR \ \(em\ The possibility of transmitting low speed anisochronous
data in Alternatives\ A and\ B is left for further study.
.RT
.sp 2P
.LP
\fB2\fR \fBLine signals\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fICarrier and guard tone frequencies\fR
.sp 9p
.RT
.PP
The carrier frequencies shall be 1200\ \(+-\ 0.5 Hz for the low channel
and 2400\ \(+-\ 1\ Hz for the high channel. A guard tone of 1800\ Hz\ \(+-\
20\ Hz, to be
transmitted only when the modem is transmitting in the high channel, may be
disabled as a national option. An alternative guard tone of 550\|\(+-\|20\
Hz may be incorporated as a national option. The question of international
calls between countries requiring different guard tones is left for further
study.
.RT
.sp 1P
.LP
2.2
\fIData and\fR
\fIguard tone\fR \fIline signal levels\fR
.sp 9p
.RT
.PP
The 1800\(hyHz guard tone shall be at a level of 6\ \(+-\ 1 dB below the
level of the data power in the high channel. The level of the optional
550\ Hz tone is for further study. The total power transmitted to line
shall be in
accordance with Recommendation\ V.2 and shall be the same for transmission in
either channel. Because of the 1800\(hyHz guard tone, the power level of data
signals in the high channel will be approximately 1\ dB lower than data
signals in the low channel.
.RT
.sp 1P
.LP
2.3
\fIFixed compromise equalizer\fR
.sp 9p
.RT
.PP
Fixed compromise equalization shall be incorporated in the modem. Such
equalization shall be equally shared between transmitter and receiver.
The characteristics of the equalizer shall be the responsibility of each
Administration to recommend nationally. The possibility of producing
compromise characteristics for international implementation is for further
study.
.RT
.sp 1P
.LP
2.4
\fISpectrum\fR and
\fIgroup\(hydelay\fR \fIcharacteristic\fR
.sp 9p
.RT
.PP
After making allowance for the nominal specified compromise
equalizer characteristic, the transmitted line signal shall have a frequency
spectrum equivalent to the
square root of a raised cosine shaping
with a 75%
roll\(hyoff
and within the limits of Figure\ 1/V.22. Similarly, the group delay of
the transmitter output shall be within \(+-\|150\ microseconds over the
frequency range 900\ Hz\(hy1500\ Hz (low channel) and 2100\ Hz\(hy2700\
Hz (high
channel). These figures are provisional.
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure\ 1/V.22, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
2.5
\fIModulation\fR
.sp 1P
.RT
.sp 1P
.LP
2.5.1
\fIData signalling rates\fR
.sp 9p
.RT
.PP
Alternatives A and B: The data signalling rate transmitted to line shall
be 1200\ bit/s or 600\ bit/s \(+-\|0.01% with a modulation rate of 600\
baud
\(+-\|0.01%.
.PP
Alternative C: In Modes i), ii), iii) and iv) (\(sc 4) the data
signalling rates are as in Alternatives A and\ B. In Mode\ v), the data
signalling rate transmitted to line shall be 1205\ \(+-\ 1\ bit/s with
a modulation rate of 602.5\ \(+-\ 0.5\ baud. Optionally in Mode v), the
line rate shall be
1223\ \(+-\ 2\ bit/s with a modulation rate of 611.5\ \(+-\ 1\ baud.
.RT
.sp 2P
.LP
2.5.2
\fIEncoding of data bits\fR
.sp 1P
.RT
.sp 1P
.LP
2.5.2.1
\fI1200 bits per second\fR
.sp 9p
.RT
.PP
The data stream to be transmitted shall be divided into groups of 2 consecutive
bits (dibits). Each dibit shall be encoded as a phase change
relative to the phase of the preceding signal element (see Table\ 1/V.22). At
the receiver, the dibits shall be decoded and the bits reassembled in correct
order. The left\(hyhand digit of the dibit is the one occurring first in
the data stream as it enters the modulator portion of the modem after the
scrambler.
.RT
.LP
.sp 1
.ce
\fBH.T. [T1.22]\fR
.ce
TABLE\ 1/V.22
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) | cw(48p) | cw(48p) .
Dibit values (1200 bit/s) Bit values (600 bit/s) T{
Phase change
(Modes i, ii, iii, iv)
T} Phase change (Mode v)
_
.T&
cw(48p) | cw(48p) | cw(48p) | cw(48p) .
00 0 +\ 90\(de +270\(de
.T&
cw(48p) | cw(48p) | cw(48p) | cw(48p) .
01 \(em \ \ \ 0\(de +180\(de
.T&
cw(48p) | cw(48p) | cw(48p) | cw(48p) .
11 1 +270\(de +\ 90\(de
.T&
cw(48p) | cw(48p) | cw(48p) | cw(48p) .
10 \(em +180\(de \ \ \ 0\(de
.TE
.LP
\fINote\fR
\ \(em\ The phase change is the actual on\(hyline phase shift in the transition region from the centre of one signalling element to the centre of the following signalling element.
.nr PS 9
.RT
.ad r
\fBTableau 1/V.22 [T1.22], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 5
.sp 1P
.LP
2.5.2.2
\fI600 bits per second\fR
.sp 9p
.RT
.PP
Each bit shall be encoded as a phase change relative to the phase of the
preceding signal element
(see\ Table\ 1/V.22).
.RT
.sp 1P
.LP
2.6
\fIReceived signal frequency tolerance\fR
.sp 9p
.RT
.PP
Noting that the frequency tolerance of the transmitter carriers is \(+-\|1\
Hz or less, and assuming a maximum shift of \(+-\|6\ Hz in the connection,
the receiver shall be able to accept errors of at least \(+-\|7\ Hz in
the received
frequencies.
.bp
.RT
.sp 2P
.LP
\fB3\fR \fBInterchange circuits\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fITable of interchange circuits\fR (Note\ 1 of Table\ 2/V.22)
.sp 9p
.RT
.PP
Essential and optional interchange circuits are listed in
Table\ 2/V.22.
.RT
.LP
.sp 2
.ce
\fBH.T. [T2.22]\fR
.ce
TABLE\ 2/V.22
.ce
\fBInterchange circuits\fR
.ce
(Note 1)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(18p) sw(180p) | cw(30p) , c | c | ^ .
Interchange circuit Notes
No. Description
_
.T&
cw(18p) | lw(180p) | lw(30p) .
102 T{
Signal ground or common return
T}
.T&
cw(18p) | lw(180p) | lw(30p) .
103 Transmitted data
.T&
cw(18p) | lw(180p) | lw(30p) .
104 Received data
.T&
cw(18p) | lw(180p) | cw(30p) .
105 Request to send Note 2
.T&
cw(18p) | lw(180p) | cw(30p) .
106 Ready for sending
.T&
cw(18p) | lw(180p) | cw(30p) .
107 Data set ready
.T&
cw(18p) | lw(180p) | cw(30p) .
108/1 Connect data set to line Note 3
.T&
cw(18p) | lw(180p) | cw(30p) .
108/2 Data terminal ready Note 3
.T&
cw(18p) | lw(180p) | cw(30p) .
109 T{
Data channel received line signal detector
T}
.T&
cw(18p) | lw(180p) | cw(30p) .
111 T{
Data signalling rate selector (DTE source)
T} Note 4
.T&
cw(18p) | lw(180p) | cw(30p) .
113 T{
Transmitter signal element timing (DTE source)
T} Note 5
.T&
cw(18p) | lw(180p) | cw(30p) .
114 T{
Transmitter signal element timing (DCE source)
T} Note 6
.T&
cw(18p) | lw(180p) | cw(30p) .
115 T{
Receiver signal element timing (DCE source)
T} Note 6
.T&
cw(18p) | lw(180p) | cw(30p) .
125 Calling indicator Note 7
.T&
cw(18p) | lw(180p) | cw(30p) .
140 Loopback/maintenance test
.T&
cw(18p) | lw(180p) | cw(30p) .
141 Local loopback
.T&
cw(18p) | lw(180p) | cw(30p) .
142 Test indicator
.TE
.LP
\fINote\ 1\fR
\ \(em\ All essential interchange circuits and any others which are provided shall comply with the functional and operational requirements of
Recommendation\ V.24. All interchange circuits provided shall be properly
terminated in the data terminal equipment and in the data circuit\(hyterminating equipment in accordance with the appropriate Recommendation for electrical
characteristics (see\ \(sc\ 3.5).
.LP
\fINote\ 2\fR
\ \(em\ Some automatic calling equipments are designed to emit a calling
tone to line by turning ON circuit\ 105 to the calling modem. The general
switched telephone network\ (GSTN) constant carrier handshake is such that no
calling tone will be emitted by the\ V.22 modem when used with these
equipments.
.LP
\fINote\ 3\fR
\ \(em\ This circuit shall be capable of operation as circuit 108/1 or 108/2 depending on its use.
.LP
\fINote\ 4\fR
\ \(em\ This circuit is optional if only the 1200 bit/s speed [modes\ i)
and\ ii) as defined in \(sc\(sc\ 4.1, 4.2 and\ 4.3] is provided in the modem. If the
600\ bit/s speed [modes\ iii) and\ iv)] is also provided, this circuit is
essential.
.LP
\fINote\ 5\fR
\ \(em\ When the modem is not operating in a synchronous mode any signals
on this circuit shall be disregarded. Many DTEs operating in an asynchronous
mode do not have a generator connected to this circuit.
.LP
\fINote\ 6\fR
\ \(em\ When the modem is not operating in a synchronous mode, this circuit shall be clamped to the OFF condition. Many DTEs operating in an asynchronous mode do not terminate this circuit.
.LP
\fINote\ 7\fR
\ \(em\ This circuit is for use with the general switched telephone network only.
.nr PS 9
.RT
.ad r
\fBTableau 2/V.22 [T2.22], + Remarques, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.bp
.sp 1P
.LP
3.2
\fICircuits 106 and 109 response times\fR \| (see Table 3/V.22)
.sp 9p
.RT
.PP
Circuit 106 response times are from the application of an ON or OFF condition
on circuit\ 105. See also \(sc\ 6 for operating sequences.
.RT
.ce
\fBH.T. [T3.22]\fR
.ce
TABLE\ 3/V.22
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(54p) | cw(54p) .
Constant carrier Controlled carrier
.T&
lw(72p) | lw(54p) | lw(54p) .
\fICircuit 106\fR
.T&
lw(72p) | cw(54p) | cw(54p) .
\ \ OFF to ON \(= 2 ms 210 to 275 ms
.T&
lw(72p) | cw(54p) | cw(54p) .
\ \ ON to OFF \(= 2 ms \(= 2 ms
_
.T&
lw(72p) | cw(54p) | cw(54p) .
\fICircuit 109\fR
.T&
lw(72p) | cw(54p) | cw(54p) .
\ \ OFF to ON 105 to 205 ms 105 to 205 ms
.T&
lw(72p) | cw(54p) | cw(54p) .
\ \ ON to OFF \ 10 to 24 ms\ \ 10 to 24 ms\
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 3/V.22 [T3.22], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.3
\fICircuit 109 thresholds\fR
.sp 9p
.RT
.PP
High channel threshold:
.RT
.LP
greater\ than\ \(em43 dBm\ \ \ circuit 109 ON
.LP
less\ than
\ \(em48 dBm\ \ \ circuit 109 OFF
.LP
Low channel threshold:
.LP
greater\ than\ \(em43 dBm\ \ \ circuit 109 ON
.LP
less\ than
\ \(em48 dBm\ \ \ circuit 109 OFF
.PP
The condition of circuit 109 between the ON and OFF levels is not specified,
except that the signal detector shall exhibit a hysteresis action
such that the level at which the OFF to ON transition occurs shall be at
least 2\ dB greater than for the ON to OFF transition.
.PP
Circuit 109 thresholds are specified at the input to the modem
excluding the effects of the compromise equalizer.
.PP
Circuit 109 shall not respond to the 1800\(hyHz or 550\(hyHz guard tones,
or the 2100\(hyHz (nominal) answer tone during the handshake sequence.
.PP
Administrations are permitted to change these thresholds where
transmission conditions are known.
.RT
.sp 1P
.LP
3.4
\fICircuit 111 and\fR
\fIdata rate control\fR
.sp 9p
.RT
.PP
Data rate selection may be by switch (or similar means) or by
circuit\ 111 or a combination of both.
.PP
The ON condition on circuit 111, where provided, shall select
1200\ bit/s operation and the OFF condition shall select 600\ bit/s
operation.
.RT
.sp 1P
.LP
3.5
\fIElectrical characteristics of interchange circuits\fR
.sp 9p
.RT
.PP
\fR Use of electrical characteristics conforming to Recommendation V.28
is recommended together with the connector and pin assignment plan specified
by ISO\ 2110.
.PP
\fINote\fR \ \(em\ Manufacturers may wish to note that the long\(hyterm
objective is to replace electrical characteristics specified in
Recommendation\ V.28, and that Study Group\ XVII has agreed that the work
shall proceed to develop a more efficient, all\(hybalanced, interface for
the V\(hySeries application which minimizes the number of interchange circuits.
.bp
.RT
.sp 1P
.LP
3.6
\fIFault condition of interchange circuits\fR
.sp 9p
.RT
.PP
(See Recommendations V.28, \(sc\ 7 for association of the receiver
failure detection types.)
.RT
.PP
3.6.1
The DTE should interpret a fault condition on circuit 107 as an
OFF condition using failure detection type\ 1.
.PP
3.6.2
The DCE should interpret a fault condition on circuits 105 and 108 as an
OFF condition using failure detection type\ 1.
.PP
3.6.3
All other circuits not referred to above may use failure detection type\
0 or\ 1.
.sp 2P
.LP
\fB4\fR \fBModes of operation over the DTE/DCE interface\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIAlternative A\fR
.sp 9p
.RT
.PP
The modem can be configured for the following modes of
operation:
.RT
.LP
Mode\ i)
1200\ bit/s\ \(+-\ 0.01% synchronous
.LP
Mode\ iii)
\ 600\ bit/s\ \(+-\ 0.01% synchronous (optional).
.PP
In these modes of operation, the modem shall accept synchronous
data from the DTE on circuit 103 under control of circuit\ 113 or circuit
114. The data shall then be scrambled in accordance with \(sc\ 5 and then
passed to
the modulator for encoding in accordance with\ \(sc\ 2.5.2.
.PP
In addition to standard V.24 transmitter timing arrangements, the
modem shall provide capabilities to derive transmit signal element timing
from receiver signal element timing.
.RT
.sp 1P
.LP
4.2
\fIAlternative B\fR
.sp 9p
.RT
.PP
The modem can be configured for the following modes of
operation:
.RT
.LP
Mode\ i)
1200\ bit/s\ \(+-\ 0.01% synchronous
Mode\ ii)
1200\ bit/s start\(hystop 8, 9, 10 or 11 bits per
character
Mode\ iii)
\ 600\ bit/s\ \(+-\ 0.01% synchronous
\(*H
.LP
\(*K\ optional
Mode\ iv)
\ 600\ bit/s start\(hystop 8, 9, 10 or 11 bits
per character
\(rb
.PP
The synchronous modes are as given in Alternative\ A.
.PP
In the start\(hystop modes, the modem shall accept a data stream of
start\(hystop characters from the DTE at a nominal rate of 1200 or 600\
bits per
second. The start\(hystop data to be transmitted shall be converted, in
conformity with Recommendation\ V.14, to a synchronous data stream suitable
for
transmission in accordance with \(sc\ 4.1
.PP
Demodulated data shall be decoded in accordance with \(sc 2.5.2, then
descrambled in accordance with \(sc\ 5 and then passed to the converter in
conformity with Recommendation\ V.14 for regaining the data stream of start\(hystop
characters.
.PP
The
intracharacter
signalling rate provided to the DTE over
circuit\ 104 shall be in the ranges given in Table\ 4/V.22 when operating
in the basic or in the extended signalling rate ranges, respectively.
.RT
.ce
\fBH.T. [T4.22]\fR
.ce
TABLE\ 4/V.22
.ce
\fBIntracharacter signalling rate range\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) sw(48p) , ^ | c | c.
Data rate Signalling rate range
Basic Extended
_
.T&
cw(48p) | cw(48p) | cw(48p) .
\ 600 bit/s \ 600 to \ 606 bit/s \ 600 to \ 614 bit/s
.T&
cw(48p) | cw(48p) | cw(48p) .
1200 bit/s 1200 to 1212 bit/s 1200 to 1227 bit/s
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 4/V.22 [T4.22], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.3
\fIAlternative C\fR
.sp 9p
.RT
.PP
The modem can be configured for the following modes of
121 (Note 4) Backward channel ready \(em \(em \(em X \(em X
122 (Note 4) T{
Backward channel received line signal detector
T} \(em \(em X \(em \(em X
125 Calling indicator X X X X X X
.TE
.LP
\fINote\ 1\fR
\ \(em\ All essential interchange circuits and any others which are provided shall comply with the functional and operational requirements of
Recommendation\ V.24. All interchange circuits indicated by\ X shall be properly terminated in the data terminal equipment and in the data circuit\(hyterminating equipment in accordance with the appropriate Recommendation for electrical
characteristics (see\ \(sc\ 9).
.LP
\fINote\ 2\fR
\ \(em\ This circuit shall be capable of operation as circuit 108/1 \(em
\fIConnect data set to line\fR
\|or circuit 108/2 \(em \fIData terminal ready\fR
depending on its use.
.LP
\fINote\ 3\fR
\ \(em\ These circuits are required when the optional clock is implemented in the modem.
.LP
\fINote\ 4\fR
\ \(em\ These circuits are not required if the modem is operating in an
asymmetrical duplex mode.
T}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/V.23 [T1.23], p. 32\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 02P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.23]\fR
.ce
TABLE\ 2/V.23
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(84p) | cw(96p) | cw(48p) .
Interchange circuit T{
Forward (data) channel
one\(hyway system
(Note 1)
T} T{
Forward data
channel either
way or both ways
simultaneously system
(Note 1)
T}
_
.TE
.TS
cw(24p) | cw(60p) | cw(24p) sw(24p) | cw(24p) sw(24p) | cw(24p) | cw(24p) , ^ | ^ | c | c | c | c | ^ | ^ .
No. Designation Without backward channel With backward channel Without backward channel With backward channel
\ \(em\ All essential interchange circuits and any others which are provided shall comply with the functional and operational requirements of
Recommendation\ V.24. All interchange circuits indicated by\ X shall be properly terminated in the data terminal equipment and in the data circuit terminating equipment in accordance with the appropriate Recommendation for electrical
characteristics (see\ \(sc\ 9).
.LP
\fINote\ 2\fR
\ \(em\ These circuits are required when the optional clock is implemented in the modem.
.nr PS 9
.RT
.ad r
\fBTableau 2/V.23 [T2.23], p. 33\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 03P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.PP
8.3.1.2
Circuit\ 106 response times are from the connection of an
ON or OFF condition on:
.LP
\(em
circuit\ 105 (where it is provided) to the appearance of the corresponding
ON or OFF condition on circuit\ 106;
.LP
\(em
circuit 122 (where circuit 105 is not provided) to the
appearance of the corresponding ON or OFF condition on
circuit\ 106 in a configuration having a single data
channel together with a single backward channel only.
.LP
\(em
circuit\ 107 (where circuits\ 105 and 122 are not provided)
to the appearance of the corresponding ON or OFF condition
on circuit\ 106;
.PP
8.3.1.3
Circuit\ 121 response times are from the connection of an
ON or OFF condition on:
.LP
\(em
circuit\ 120 (where it is provided) to the appearance of the corresponding
ON or OFF condition on circuit\ 121;
.LP
\(em
circuit\ 109 (where circuit\ 120 is not provided) to the
appearance of the corresponding ON or OFF condition on
circuit\ 121.
.sp 1P
.LP
8.3.2
\fIResponse times\fR
.sp 9p
.RT
.ce
\fBH.T. [T3.23]\fR
.ce
TABLE\ 3/V.23
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(72p) | lw(78p) | lw(78p) .
\fICircuit 106\fR
.T&
lw(72p) | lw(78p) | lw(78p) .
\ \ OFF to ON T{
750 ms to 1400 ms (see Note 1)
T} T{
a)
\ 20 ms to \ 40 ms
(see Note 2)
b)
200 ms to 275 ms
(see Note 2)
T}
.T&
lw(72p) | cw(156p) .
\ \ ON to OFF \(= 2 ms
_
.T&
lw(72p) | lw(84p) | lw(72p) .
\fICircuit 109\fR
.T&
lw(72p) | lw(84p) | lw(72p) .
\ \ OFF to ON 300 ms to 700 ms (see Note 1) T{
\ 10 ms to \ 20 ms (see Note 1)
T}
.T&
lw(72p) | cw(156p) .
\ \ ON to OFF 5 ms to 15 ms
_
.T&
lw(72p) | cw(156p) .
\fICircuit 121\fR
.T&
lw(72p) | cw(156p) .
\ \ OFF to ON 80 ms to 160 ms
.T&
lw(72p) | cw(156p) .
\ \ ON to OFF \(= 2 ms
_
.T&
lw(72p) | cw(156p) .
\fICircuit 122\fR
.T&
lw(72p) | cw(156p) .
\ \ OFF to ON < 80 ms
.T&
lw(72p) | cw(156p) .
\ \ ON to OFF 15 ms to 80 ms
.TE
.LP
\fINote\ 1\fR
\ \(em\ For automatic calling and answering, the longer response times of
circuits 106 and 109 are to be used during call establishment only.
.LP
\fINote\ 2\fR
\ \(em\ The choice of response times depends upon the system
application:
a)\ no protection given against line echoes;
b)\ protection given against line echoes.
.LP
\fINote\ 3\fR
\ \(em\ The above parameters are provisional and are the subject of
further study.
.nr PS 9
.RT
.ad r
\fBTableau 3/V.23 {T3.23] + remarques], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 1
.bp
.sp 1P
.LP
8.4
\fIThreshold of data channel and backward channel received line\fR
\fIsignal detectors\fR
.sp 9p
.RT
.PP
Level of received line signal at receive line terminals of modem
for all types of connections, i.e. general switched telephone network or
non\(hyswitched leased telephone circuits:
.RT
.LP
greater\ than\ \(em43\ dBm\ \ \ \ circuits 109/122 ON
.LP
less\ than
\ \(em48\ dBm\ \ \ \ circuits 109/122 OFF
.PP
The condition of circuits\ 109 and 122 for levels between \(em43\ dBm and
\(em48\ dBm is not specified except that the signal detectors shall exhibit
a hysteresis action such that the level at which the OFF to ON transition
occurs is at least 2\ dB greater than that for the ON to OFF transition.
.PP
Where transmission conditions are known on switched or leased
circuits, Administrations should be permitted at the time of modem installation
to change these response levels of the received line signal detectors to
less sensitive values (e.g. \(em33\ dBm and \(em38\ dBm respectively).
.RT
.sp 1P
.LP
8.5
\fIClamping\fR \fIin half\(hyduplex mode\fR
.sp 9p
.RT
.PP
The DCE, when operating in half\(hyduplex mode on a 2\(hywire line,
shall hold, where implemented:
.RT
.LP
i)
circuit 104 in the binary 1 condition and circuit 109
in the OFF condition when circuit 105 is in the ON condition
and, where required to protect circuit 104 from false signals,
for a period of 150\ \(+-\ 25 milliseconds following the ON to OFF
transition on circuit\ 105. The use of this additional delay
is optional, based on system considerations;
.LP
ii)
circuit 119 in the binary 1 condition and
circuit\ 122 in the OFF condition when circuit\ 120 is in
the ON condition and, where required to protect circuit\ 119
from false signals, for a time interval following the ON
to OFF transition on circuit\ 120. The specific duration
of this time interval is left for further study. The
additional delay is optional, based on system considerations.
.sp 1P
.LP
8.6
\fIFault condition of interchange circuits\fR
.sp 9p
.RT
.PP
(See Recommendation V.28, \(sc\ 7 for association of the receiver
failure detection types).
.RT
.PP
8.6.1
The DTE should interpret a fault condition on
circuit 107 as an OFF condition using failure detection type\ 1.
.PP
8.6.2
The DCE should interpret a fault condition on
circuits 105 and 108 as an OFF condition using failure detection type\ 1.
.PP
8.6.3
All other circuits not referred to above may use
failure detection types\ 0 or\ 1.
.sp 2P
.LP
\fB9\fR \fBElectrical characteristics of interchange circuits\fR
.sp 1P
.RT
.PP
Use of electrical characteristics conforming to
Recommendation\ V.28 is recommended together with the connector pin
assignment plan specified by ISO\ 2110.
.PP
\fINote\fR \ \(em\ Manufacturers may wish to note that the long\(hyterm
objective is to replace electrical characteristics specified in
Recommendation\ V.28, and that Study Group\ XVII has agreed that the work
shall proceed to develop a more efficient, all balanced, interface for
the V\(hySeries application which minimizes the number of interchange circuits.
.RT
.sp 2P
.LP
\fB10\fR \fBEquipment for the\fB
\fBdisablement of echo suppressors\fR
.sp 1P
.RT
.PP
When
echo control device disabling
is required, it is
recommended that the procedures specified in Recommendation\ V.25 be
followed.
.bp
.RT
.sp 2P
.LP
\fB11\fR \fBInclusion of a clock in the modem\fR
.sp 1P
.RT
.PP
A clock is not an essential item in the standardized modem.
However, the modem may conveniently include a clock when used primarily for
synchronous transmission.
.PP
If such a clock is included in the modem, a synchronizing pattern
consisting of alternate binary\ 0 and binary\ 1 at clock rate should be
transmitted for the whole interval between the OFF to ON transitions of
interchange circuits\ 105 and 106. Users should note that part of this
synchronizing pattern may appear at the distant receiver on circuit\ 104
after the OFF to ON transition of circuit\ 109. The data terminal equipment
should make provision to differentiate between these false signals and true
data.
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIStandardization of FMVFT systems for a\fR
\fImodulation rate of 50\ bauds\fR , Vol.\ VII, Rec.\ R.35.
.LP
.rs
.sp 40P
.ad r
BLANC
.ad b
.RT
.sp 2P
.LP
\fBMONTAGE:\ \ \ \fR Rec. V.24 sur le reste de cette page.