AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 164

Applications
Far-End Disconnect
When a far-end disconnect signal is detected on an outside line/trunk on which
a call is made to or received from a VMI port, the system sends the disconnect
signal to the VMI port, whether or not that port is the only party left on the call. If
another party is still on the call, the VMS decides whether to continue or
disconnect the party. (The far-end disconnect signal occurs only if the
LS/GS/DID/Tie VMI port is programmed for reliable disconnect.)
Ports In/Out of Service
When a calling group call to a VMI port is not answered within 30 seconds, the
call is sent to another available VMI port in the calling group or is queued back
to wait for an available port in the calling group.
For an integrated VMI port, the control unit sends mode codes to inform the
VMS that the port is out of service. Both the VMS and the calling group software
mark the unavailable port out-of-service. If all VMI ports go out of service, a
programming logic inconsistency (PLI) is generated.
Every 10 minutes the system tests each out-of-service VMI port. If the port
responds to the test, the VMS and the calling group software mark it in-service.
For an integrated VMI port, the control unit informs the VMS by sending port-in-
service mode codes.
4-8 Voice Messaging Systems