Signaling - Avaya S8700 Maintenance Manual

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Signaling

This section describes disconnect supervision and transmission characteristics.

Disconnect Supervision

Disconnect supervision means the CO has the ability to release a trunk when the

party at the CO disconnects and the system is able to recognize the release

signal. In general, a CO in the United States provides disconnect supervision for

incoming calls but not for outgoing calls. Many other countries do not provide

disconnect supervision for either incoming or outgoing calls.

The system must provide the assurance that at least one party on the call can

control dropping the call. This avoids locking up circuits on a call where no party

is able to send a disconnect signal to the system. Internal operations must check

to be sure one party can provide disconnect supervision. An incoming trunk that

does not provide disconnect supervision is not allowed to terminate to an outgoing

trunk that does not provide disconnect supervision.

In a DCS environment, an incoming trunk without disconnect supervision can

terminate to an outgoing DCS trunk connecting two nodes. The incoming trunk is

restricted from being transferred to a party without disconnect supervision on the

terminating node. This is because, through messaging, the terminating node

knows the originating node cannot provide disconnect supervision. This

messaging is not possible with non-DCS tie trunks, and the direct call is denied.

Some 2-wire loop start trunks outside the United States provide busy tone

disconnect in place of line signals. For these trunks, an adjunct can be attached

to the trunk to listen for busy or other disconnect tone. When a tone is detected,

the adjunct sends line signals for disconnect to the system.

Administration is provided for each trunk group to indicate whether it provides

disconnect supervision for incoming calls and for outgoing calls.

Transfer on Ringing

A station or attendant may conference in a ringing station or transfer a party to a

ringing station. When a station conferences in a ringing station and then drops

the call, the ringing station is treated like a party without disconnect supervision.

However, when a station transfers a party to a ringing station, the ringing station

party is treated like a party with disconnect supervision. Two timers (Attendant

Return Call Timer and Wait Answer Supervision Timer) are provided to ensure the

call is not locked to a ringing station.

Issue 1 May 2002