H3C Technologies H3C MSR 5600 - Manual (Page 47)

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• Blocking in idle state or during conversation.
After the originating side receives a blocking signal 11 from the terminating side when the circuit
is idle or during conversation, the circuit is blocked. In this case, the originating side still sends the
forward signal 10 to indicate that the line is idle. When the terminating side unblocks the circuit,
it sends a backward signal 10 to indicate that the line is idle. The originating side maintains the
forward signal 10 and unblocks the local-end circuit for the next call.
ITU-T interregister signaling
Interregister signaling transmits and requests calling and called numbers. It adopts the multi-frequency
compelled (MFC) mode and includes forward signaling and backward signaling. Forward signaling
exchange includes Group I and Group II, and backward signaling exchange includes Group A and
Group B. When the originating side recognizes the seizure acknowledgement signal, interregister
signaling begins to send the first digit of the called number, and waits for the response of Group A
signaling from the terminating side.
• Group I forward signals—Include connection control signals and digit signals.
Table 4 Forward Group I signals
Designation Basic meaning
I-1 through I-10
Digits 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0, responsible for sending number
information to the terminating side
I-11 Spare for national use
I-12 Request refused
I-13 Connected to tested device
I-14 Spare for national use
I-15
Address identification terminator and pulse terminator (used in
international calls)
• Group A backward signals—Control signals used for controlling and acknowledging Group I
forward signals.
Table 5 Group A backward signals
Designation Basic Meaning
A-1 Send next digit
A-2 Send last but one digit
A-3 Address-complete; changeover to reception of Group B signals
A-4 Congestion in the national network
A-5 Send calling party's category
A-6 Address-complete, charge, and set up speech conditions
A-7 Send last but two digits
A-8 Send last but three digits
A-9 Spare for national use
A-10 Spare for national use
A-11 Send country code indicator