(5.1)\ \ For circuits on switched telegraph networks, the conditions of
Recommendation\ U.20\ [2] should apply. In this usage the polarity retransmitted
by the terminal of the radio channel towards the start\(hystop section
of the
circuit during a repetition cycle shall be start polarity when the circuit
is in the \*Qfree line\*U condition and stop polarity when the circuit
is in the \*Qbusy circuit\*U condition.
.PP
(5.2)\ \ For point\(hyto\(hypoint circuits, Administrations may adopt, at the
terminal equipment under their jurisdiction, their own method of stopping
and starting the motors of the receiving machines, based on Recommendation\
S.7.
Signal\ \(*b should normally be transmitted to indicate the idle circuit
condition. However, for signalling purposes, the signals\ \(*a and\ \(*b may be
employed.
\v'6p'
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation\ S.13)
.sp 9p
.RT
.ce 0
.LP
A.1
\fIConversion table\fR
.sp 1P
.RT
.PP
A.1.1
Table\ A\(hy1/S.13 shows the correspondence between International
Telegraph Alphabet\ No.\ 3 used in 7\(hyunit ARQ\ systems and International
Telegraph Alphabet\ No.\ 2 (defined in the Recommendation cited in\ [5]).
.sp 9p
.RT
.sp 2P
.LP
A.2
\fIRepetition cycles\fR
.sp 1P
.RT
.PP
A.2.1
Four characters for normal circuits that are not subject to
excessive propagation time. The cycle should comprise one
signal
repetition
and three stored characters.
.sp 9p
.RT
.PP
A.2.2
Eight characters on circuits for which the four\(hycharacter
repetition cycle is inadequate. The cycle should comprise one signal
repetition, three signals\ \(*b and four stored characters, or one signal
repetition and seven stored characters.
.LP
A.3
\fIChannel arrangement\fR
.sp 1P
.RT
.sp 2P
.LP
A.3.1
\fIChannel A\fR
.sp 1P
.RT
.PP
A.3.1.1
For equipments employing a 4\(hycharacter repetition cycle:\ one
character inverted followed by three characters erect [see\ (a) of
Figure\ A\(hy1/S.13].
.sp 9p
.RT
.PP
A.3.1.2
For equipments employing an 8\(hycharacter repetition cycle:\ one
character inverted followed by seven characters erect [see\ (a) of
Figure\ A\(hy2/S.13].
.sp 2P
.LP
A.3.2
\fIChannel B\fR
.sp 1P
.RT
.PP
A.3.2.1
For equipments employing a 4\(hycharacter repetition cycle:\ one
character erect followed by three characters inverted [see\ (b) of
Figure\ A\(hy1/S.13].
.sp 9p
.RT
.PP
A.3.2.2
For equipments employing an 8\(hycharacter repetition cycle:\ one
character erect followed by seven characters inverted [see\ (b) of
Figure\ A\(hy2/S.13].
.sp 2P
.LP
A.3.3
\fIChannel C\fR
.sp 1P
.RT
.PP
As for Channel\ B [see (c) of Figures\ A\(hy1/S.13 and\ A\(hy2/S.13].
.RT
.sp 2P
.LP
A.3.4
\fIChannel D\fR
.sp 1P
.RT
.PP
As for Channel\ A [see (d) of Figures\ A\(hy1/S.13 and\ A\(hy2/S.13].
.bp
.RT
.LP
.rs
.sp 35P
.ad r
\fBCuadro A\(hy1/S.13 [T1.13], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
A.3.5
\fIOrder of transmission\fR
.sp 1P
.RT
.PP
A.3.5.1
Characters of Channels\ A and\ B are transmitted consecutively
[see (e) of Figures\ A\(hy1/S.13 and\ A\(hy2/S.13].
.sp 9p
.RT
.PP
A.3.5.2
Elements of Channel C are interleaved with those of Channel A
[see (g) of Figures A\(hy1/S.13 and
A\(hy2/S.13].
.PP
A.3.5.3
Elements of Channel D are interleaved with those of Channel B
[see (g) of Figures A\(hy1/S.13 and
A\(hy2/S.13].
.PP
A.3.5.4
In the aggregate signal, A\ elements precede those of C, and
B\ elements precede those of\ D [see\ (g) of Figures\ A\(hy1/S.13 and\
A\(hy2/S.13].
.PP
A.3.5.5
The first erect character on A, transmitted after the inverted
character on A, is followed by the erect character on B [see\ (e) of
Figures\ A\(hy1/S.13 and\ A\(hy2/S.13].
.PP
A.3.5.6
The erect character on C is followed by the inverted character
on D [see (f
) of Figures\ A\(hy1/S.13 and\ A\(hy2/S.13].
.PP
A.3.5.7
The inverted character on A is element\(hyinterleaved with the
erect character on C [see (g) of Figures
A\(hy1/S.13 and\ A\(hy2/S.13].
.bp
.sp 2P
.LP
A.4
\fISubchannel arrangement\fR
.sp 1P
.RT
.PP
A.4.1
The character transmission rate of the fundamental subchannel should be
a quarter of the standard character rate.
.sp 9p
.RT
.PP
A.4.2
Subchannels should be numbered 1, 2, 3 and 4 consecutively.
.PP
A.4.3
Where a 4\(hycharacter repetition cycle is used, subchannel\ 1
should be that subchannel which has opposite\ keying polarity to
the other three subchannels of the same main channel [see (a), (b), (c)
and (d) of Figure\ A\(hy3/S.13]. When an 8\(hycharacter repetition cycle
is used,
subchannel\ 1 should be that subchannel which has alternately erect and
inverted keying polarity [see\ (e), (f
), (g) and\ (h) of Figure\ A\(hy3/S.13].
.PP
A.4.4
When subchannels of half\(hycharacter rate, or
three\(hyquarter\(hycharacter rate are required, combinations of the fundamental
subchannels should be arranged as shown in Table\ A\(hy2/S.13.
.sp 2P
.LP
A.5
\fIDesignation of aggregate signal\fR
.sp 1P
.RT
.PP
To assist in identifying the signal condition when applying the
aggregate telegraph signal to modulate the radio channel, the designation
for the aggregate signal should be used as shown in Table\ A\(hy3/S.13.
.RT
.sp 2P
.LP
A.6
\fIDiagrams\fR
.sp 1P
.RT
.PP
As a result of the characteristics specified in \(sc\(sc\ A.2, A.3 and\
A.4 above, the transmission of characters will be as shown in Figures\
A\(hy1/S.13,
A\(hy2/S.13 and\ A\(hy3/S.13.
.RT
.sp 2P
.LP
A.7
\fIAutomatic phasing\fR
.sp 1P
.RT
.PP
A.7.1
Automatic phasing should normally be used. It should be
initiated either:
.sp 9p
.RT
.LP
a)
after a waiting period during which cycling due to the
receipt of errors has occurred continuously on both channels on a 2\(hychannel
system, or on at least two main channels of a 4\(hychannel system;
.LP
b)
after equal counts of A and Z elements have been made
over at least two consecutive system cycles whilst continuous cycling due to
the receipt of errors is occurring on all main channels.
.PP
A.7.2
When the slave station is phasing, it should transmit in each
channel, in place of the signal repetition, a 7\(hyelement signal in which all
seven elements are of the same polarity, all other characters in the repetition
cycle being transmitted unchanged.
.LP
.rs
.sp 19P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy1/S.13 p. 10\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy2/S.13 p. 11\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy3/S.13 p. 12\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.13]\fR
.ce
TABLE\ A\(hy2/S.13
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(60p) .
{
Proportion of full\(hychannel character rate
} {
Combination of fundamental subchannels
}
_
.T&
lw(60p) | lw(60p) .
(1)\ quarter No. 1
.T&
lw(60p) | lw(60p) .
(2)\ quarter No. 3
.T&
lw(60p) | lw(60p) .
(3)\ half Nos. 2 and 4
_
.T&
lw(60p) | lw(60p) .
(1)\ half Nos. 1 and 3
.T&
lw(60p) | lw(60p) .
(2)\ half Nos. 2 and 4
_
.T&
lw(60p) | lw(60p) .
(1)\ quarter No. 1
.T&
lw(60p) | lw(60p) .
(2)\ three\(hyquarters Nos. 2, 3 and 4
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau A\(hy2/S.13 [T2.13], p. 13\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.ce
\fBH.T. [T3.13]\fR
.ce
TABLE\ A\(hy3/S.13
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(42p) sw(42p) , ^ | c | c.
Seven\(hyunit code condition Aggregate signal condition
Erect character Inverted character
_
.T&
cw(60p) | cw(42p) | cw(42p) .
A B Y
.T&
cw(60p) | cw(42p) | cw(42p) .
Z Y B
.TE
.LP
\fINote\fR
\ \(em\ With a frequency shift system, the higher frequency should correspond to aggregate condition B and the lower frequency should correspond to aggregate condition Y.
.nr PS 9
.RT
.ad r
\fBTableau A\(hy3/S.13 [T3.13], p. 14\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fITelex and gentex signalling on intercontinental\fR
\fIcircuits used for intercontinental automatic transit traffic (Type\
C\fR
\fIsignalling)\fR , Rec.\ U.11.
.LP
[2]
CCITT Recommendation \fITelex and gentex signalling on radio channels\fR
\fI(synchronous 7\(hyunit systems affording error correction by automatic\fR
\fIrepetition)\fR , Rec.\ U.20.
.LP
[3]
CCITT Recommendation \fIOperator recall on a telex call set up on\fR
\fIradiotelegraph circuit\fR , Rec.\ U.21.
.LP
[4]
CCITT Recommendation \fISignals indicating delay in transmission on\fR
\fIcalls set up by means of synchronous systems with automatic error correction\fR
\fIby repetition\fR , Rec.\ U.22.
.LP
[5]
CCITT Recommendation \fIOperational provisions for the international\fR