HP FlexNetwork MSR Series Configuration Manual page 87

After the terminating side receives a forward signal 11 from the originating side to indicate
device fault during conversation, the terminating side releases the line backward. At the same
time, it sends a backward signal 11. Then, the circuit is in faulty state. When the device recovers,
the originating side sends a forward signal 10, and the terminating side sends back a signal 10.
At this time, the circuit recovers.
ITU-T interregister signaling
Interregister signaling controls automatic connection of circuits. It adopts MFC mode and includes
forward signaling and backward signaling. Forward signaling exchange includes Group I and Group
II, while backward signaling exchange includes Group A and Group B. When the originating side
recognizes the seizure acknowledgement signal, the register 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 7 Forward Group I signals
Designation
I-1 through I-10
I-11
I-12
I-13
I-14
I-15
•
Group A backward signals—Control signals used for controlling and acknowledging Group I
forward signals.
Table 8 Group A backward signals
Designation
A-1
A-2
A-3
A-4
A-5
A-6
A-7
A-8
A-9
A-10
A-11
A-12
A-13
A-14
Basic meaning
Digits 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0, responsible for sending number
information to the terminating side
Spare for national use
Request refused
Connected to tested device
Spare for national use
Address identification terminator and pulse terminator (used in
international calls)
Basic Meaning
Send next digit
Send last but one digit
Address-complete; changeover to reception of Group B signals
Congestion in the national network; terminate interregister signaling exchange
Send calling party's category
Address-complete; terminate interregister signaling exchange, charge, and set
up speech conditions
Send last but two digits
Send last but three digits
Spare for national use
Spare for national use
Send country code indicator
Send language or discrimination digit
Send nature of circuit
Request for information on use of an echo canceller
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