AT&T MERLIN LEGEND Release 4.0 Feature Reference page 555

Feature Reference
Considerations and Constraints
Extensions do not need to be renumbered in the following cases:
The default 2-digit extension numbers are acceptable.
No special extension numbers are needed.
There are fewer than 50 extensions in the system.
Any extension number except 0 (system operator) can be renumbered. Trunk
numbers (801–880) can be renumbered.
After an extension is renumbered, the original extension number is available for
use. For example, after extension 32 is renumbered to 40, extension 32 is
available for use.
System renumbering should not be confused with board renumbering, which is
used when modules in the control unit are changed. For additional information
about board renumbering, see System Programming .
When you use system renumbering in Release 2.0 or earlier with Integrated
Solution III version 1.0 or 1.1, AUDIX Voice Power erases all messages and
greetings for extensions that have been renumbered. This occurs when the
automatic reconciliation program runs at 3:00 a.m. The reconciliation program is
disabled in Integrated Solution III version 1.2.
Feature Interactions
Authorization Code
Automatic Route
Selection
Ringing/Idle Line
Preference
Authorization codes are associated with logical IDs, not extension
numbers. If extensions are renumbered and the logical IDs for the
extensions change, the authorization codes may be reassigned to
different extensions.
In Hybrid/PBX mode, the Automatic Route Selection (ARS) access code
(factory setting is 9) can be renumbered.
In Key and Behind Switch modes, the Idle Line Access code (factory
setting is 9) can be renumbered.
System Renumbering
555