User guide

August 2001 27
Defining Digit Types
Group A Signals
The incoming register sends Group A signals in
acknowledgment to the Group I signals sent by the outgoing
register. These signals request additional information from the
transmitting end. Signals A-3 and A-5 prepare the outgoing
register to both receive Group B signals and send Group II
signals. Systems that use 6 or 10 backward signals have
significantly different meaning for the signals. Table 9 shows
the meanings of the Group A signals in a system that uses 15
signals.
Table 9. Group A Signals
Signal Meaning
1 Send next digit (n+1)
2 Send last but one digit (n-1)
3 Change to receive Group B signals
4 Congestion in the national network
5 Send calling party’s category
6 Address complete, charge, set up speech conditions
7 Send last but two digit (n-2)
8 Send last but three digit (n-3)
9 Spare for national use
10 Spare for national use
11 Send country code indicator
12 Send language or discriminating digit
13 Send nature of circuit
14 Request information about whether an incoming
half-echo suppressor is required
15 Congestion in an international exchange or at its
output