Lucent Technologies 555-661-150 manual Tandem Facilities

MERLIN LEGEND Communications System Release 6.1	Issue 1
Network Reference 555-661-150	August 1998
1 Introduction
Centralized Voice Messaging System	Page 1-22

■Only the following voice messaging systems are supported for centralized VMS/AA:

■MERLIN LEGEND Mail

■Messaging 2000

■Intuity AUDIX

■IS-III AUDIX Voice Power (no longer orderable)

■A Uniform Dial Plan (UDP) must be established for the private network.

■All trunks within the private network should have unique trunk numbers. This allows the centralized VMS/AA to provide different call handling and/or greetings based on the trunk on which the call was received.

■No more than three (3) analog spans should be involved in any call or volume levels may not be adequate. Multiple spans may be the result of transfers and coverage. If more than three spans may be involved in call completion, digital rather than analog spans should be used.

■Sending overflow or coverage calls to a centralized VMS/AA may add unanticipated traffic to a private network. A call transferred from one system to another and then sent back by overflow or coverage occupies two private network trunks. The MERLIN LEGEND system does not provide release link operation when a call through the private network returns to the originating system.

■Pools within a UDP route cannot mix PRI and tie tandem trunks. The type of signaling is based on the first trunk in the pool, and will not work correctly for subsequent trunks if they are not the same type.

■If tandem tie trunks are used, touch tone receivers (TTR) are required at the hub system and at each remote system for each call (including coverage calls) and for message-waiting light updates over the tie trunks. Voice messaging increases traffic in both directions.

Tandem Facilities 1

MERLIN LEGEND systems are connected by tandem trunks. Tandem trunks may be tie trunks or PRI trunks:

■A tie trunk may be analog (E & M) or digital (T1). An analog tie trunk carries a single voice call channel. A digital (T1 or fractional T1) tie trunk carries up to 24 voice call channels using a digital encoding scheme. Both use in- band signalling.

■A PRI tandem trunk is a point-to-point T1 circuit programmed in the MERLIN LEGEND systems at both ends as ISDN Primary Rate Interface (PRI). It consists of 23 B-channels for voice calls (digitally encoded) and 1 D-channel (channel 24) for digital signalling information.

The type of tandem trunk used (PRI or tie) has an effect on the operation of the centralized VMS/AA system.