Signaling; Disconnect Supervision - Avaya MCC1 Maintenance Procedures

origination or destination system. A modem-pool member is always inserted automatically for
calls to off-premises sites via analog or voice-grade trunking. For internal calls, however, the
systems are capable of automatically inserting a modem-pool member.
• Data cannot be carried over analog facilities unless inside the system it is represented as a PCM-
encoded analog signal. To do this for data originating at a digital terminal, the signal enters the
system at a digital port and exits the system at a digital port. The signal then reenters the system
through a modem-pool connection (data-module to modem to analog-port) and exits the system
again at an analog port.
• Although DS1 is commonly called a trunk speed, here it names the protocol used at layer 1 for
digital trunks. Some trunks use different signaling methods but use DS1 protocol at layer 1 (for
example, PRI and 24th-channel signaling trunks).

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 ensure that 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 that the originating node cannot provide disconnect supervision. This messaging
is not possible with non-DCS tie trunks, and the direct call is denied.
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.
Maintenance Procedures
December 2003
Maintenance strategy
Signaling
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