3Com MSR 50 Series Configuration Manual page 2322

2322 C 134: E1
HAPTER AND
T1 C
ONFIGURATION
Figure 674 R2 digital line signaling - terminating point releases the call
Originating point Originating point Originating point Originating point
Talk Talk
Clear-back Clear-back
Clear-forward Clear-forward
Release-guard Release-guard
Line released by forced release signal: When the terminating point supports
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metering signals, the system may send a forced release signal 00 instead of a
clear-back signal 11 to release the line. This is to avoid collision between the
clear-back signal sent by the called party and the metering signal.
Blocking in idle state or during conversation: After the originating point
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receives a blocking signal 11 from the terminating point when the trunk circuit
is idle or during conversation, it sends a forward signal 10. At this time, the
trunk circuit is blocked. When the terminating point unblocks the trunk circuit,
it sends a backward signal 10 in the corresponding line to indicate that the line
is idle. The originating point should maintain the forward signal 10 and
unblock the local-end trunk circuit for next call.
Troubleshooting in idle state: If the terminating point receives a forward signal
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11 from the originating point to indicate device fault when the trunk circuit is
idle, the terminating point sends a backward signal 11. Then, the trunk circuit
is in faulty state. When the device recovers, the originating point sends the
forward signal 10, and the terminating point responds with the signal 10. At
this time the trunk circuit regains normal state.
Troubleshooting during conversation: After the terminating point receives a
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forward signal 11 from the originating point to indicate device fault during
conversation, the terminating point releases the line backward. At the same
time, it sends a backward signal 11. Then, the trunk circuit is in faulty state.
When the device recovers, the originating point sends a forward signal 10, and
the terminating point sends back a signal 10. At this time, the trunk circuit
recovers.
2 ITU-T interregister signaling
Interregister signaling controls automatic connection of circuits. It adopts MFC
mode and falls into forward signaling and backward signaling. Forward signaling
exchange falls into Group I and Group II, while backward signaling exchange falls
into Group A and Group B. When the originating point 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
point.
Group I forward signals: include connection control signals and digit signals.
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Terminating point Terminating point Terminating point Terminating point