Lucent Technologies 555-661-150 manual Automatic Route Selection ARS

MERLIN LEGEND Communications System Release 6.1	Issue 1
Network Reference 555-661-150	August 1998

2Call-Handling Scenarios

Networking Guidelines Page 2-7

must be prepended. Furthermore, users on your system dial only four digits to reach remote extensions while DEFINITY ECS or DEFINITY ProLogix Solutions users dial five digits for intercom calls within their local systems, so extension numbering is not consistent across the private network.

When a private network includes a DEFINITY ECS or DEFINITY ProLogix Solutions system, it is recommended that the MERLIN LEGEND Communications Systems in the private network use 4-digit extension numbers in their local dial plans. One reason is that DEFINITY ECS and DEFINITY Prologix Solutions systems cannot dial anything less than a 4-digit extension number. If a DEFINITY ECS or DEFINITY ProLogix Solutions system is the hub and uses 5-digit extension numbers, calls can be more easily routed through it to reach MERLIN LEGEND Communications System extension numbers that are four digits long. If the MERLIN LEGEND Communications System extension numbers are three digits long, there are more potential numbering conflicts. For example, if a MERLIN LEGEND Communications System extension number range is 220–249, it can conflict with a very large range of DEFINITY ECS or DEFINITY ProLogix Solutions system extension numbers, 22000–24999. Furthermore, 4-digit numbering provides more room for growth and for easy routing to different types of extensions in a MERLIN LEGEND Communications System, without the need for system renumbering of the local dial plan.

When planning for centralized VMS/AA, keep in mind that the DEFINITY ECS and DEFINITY ProLogix Solutions systems cannot send coverage or overflow calls to a VMS/AA on a MERLIN LEGEND system, and a MERLIN LEGEND system cannot send coverage or overflow calls to a DEFINITY system’s VMS/AA. The automated attendants on both systems can transfer calls to extensions on the other system. The position of the DEFINITY system within the private network may also affect the ability of MERLIN LEGEND systems to use a centralized VMS/AA. Only a MERLIN LEGEND system directly connected by tandem trunks to the MERLIN LEGEND system where the centralized VMS/AA is installed can send calls to the centralized VMS/AA.

Automatic Route Selection (ARS) 2

Local system users may use ARS to route calls over tandem trunks to the PSTN facilities connected to a remote system.

This arrangement can provide toll cost savings when users need to reach outside numbers that are not in their own local calling area but are local to other systems in a private network. It also means that in some cases, a MERLIN LEGEND Communications System may have only one or two PSTN trunks connected to it for emergency purposes only. Under normal circumstances, the system uses PSTN facilities connected to another system in the private network, which can provide call-volume advantages when buying PSTN services such as domestic long-distance calling. The scenarios later in this chapter provide examples.