Specifications

Legacy Integration
Planning and Installation Guide 14 – 3
Trunk Requirements
The number of digital trunks required between the ShoreTel 6.1 system and the legacy
PBX depends on the expected traffic between the two systems. To determine the
number of trunks, you need to estimate the number of calls per hour that are placed
between the two systems. When estimating the call volume between the two systems,
consider the following:
• The volume of direct calls between users on the two systems
• Traffic related to Automated Call Distributor (ADC) calls
• Outbound call volume (i.e. when outbound trunking to the PSTN is provided by
one of the systems for all users, such as a PSTN trunk connected to the legacy PBX
that provides long distance services for users on both the legacy and ShoreTel 6.1
system)
• Inbound call volume (i.e. when inbound services are provided by one system to all
users)
Additionally, you can rely on the estimated calls-per-hour number to determine the
number of trunks to configure between the two systems.
For more information on trunk requirements, see Chapter 5, “Trunk Planning and
Ordering.”
Coordinated Dialing Plan
With legacy integration, users on both systems can dial one another using abbreviated
or extension dialing. This includes dialing from applications on the systems, such as
the ShoreTel 6.1 voice mail application, or also includes forwarding a call to an
assistant at an extension on the legacy PBX. To determine the coordinated dialing plan
configuration, you must identify the current numbering of users on both systems. For
example:
• When the systems are located together, extensions can normally be assigned from
a single numbering plan, or from a single DID number range provided by the local
carrier. In this case, the extensions on the two systems are assigned such that there
is no overlap using the desired extension length.
• When systems are at different locations, each system’s numbering plan is often
based on the DID range supplied by the local telephone company. In this case,
overlap of the extension ranges can occur at the currently used extension length.
For example, consider the following situation.
• One location is assigned DID range 408-555-2000 through 2999
• The second location is assigned range 650-333-2500 through 2799
• The systems currently use four-digit dialing matching the DID numbers.
In this case, there are users on both systems currently assigned extension 2500. To
provide a coordinated dialing plan across the systems, the extensions must be adjusted
to make them unique system-wide. In the integration, four-digit extensions that
overlap are made unique by increasing the extension length across the system. When
the extension length is increased, the first digit becomes the “system” number and the
remaining digits are the “extension.” In the above example, the extension length would
be increased to five-digit dialing, and at the first location would be extensions 52000