AT&T MERLIN LEGEND Communications System PBX System Planning Manual page 49

Control Unit
System Renumbering
Two-Digit Numbering Plan
2-20 System Numbering
Use these instructions to decide whether to keep the factory-set extension
numbers or change them to numbers tailored to your company—for
example, extension numbers that match room numbers.
The system offers three numbering plans, as shown on Form 2a, System
Numbering — Station Jacks. Each plan allows you to renumber all or selected
extensions:
Two-Digit- designed for systems with fewer than 50 stations at businesses
that do not anticipate growth to more than 50 stations in the next one or two
years. The two-digit numbering plan is the factory setting.
Three-Digit- designed for businesses with more than 50 stations.
Set Up Space- designed for businesses that want to customize numbering
and assign 1- to 4-digit extensions that are more convenient for users. As an
example, hotels and motels may want to renumber extensions to match room
numbers and to renumber services numbers (such as Housekeeping or
Room Service) to 1-digit extension numbers.
When you reassign extension numbers, keep the following in mind:
Extension numbers can contain the digits O through 9 in any combination,
except that no extension number can begin with O. (The O is a fixed dial code
representing the primary operator.)
Extension numbers can contain one to four digits and must be unique. If you
assign an extension number with one or two digits, you cannot use those
digits as the leading digits for a longer extension number. For example, if you
assign extension numbers 1, 2, 30, and 40, you cannot use those numbers
as the first number in longer extension numbers such as 10, 200, 302, or
4052.
The system-assigned numbers in the shaded areas of the figures on the
following pages are automatically reserved. To use any of these numbers for
a different station, you must assign a new extension to the station that
already has the number you need to use.
When you reassign an extension number, the extension number vacated is
free for you to use.
Select the numbering plan that fits your needs and use the appropriate
plan-specific instructions that follow to mark Forms 2a and 2b with your
extension number assignments
The extension numbers you assign according to the factory-set two-digit
numbering plan are shown in Figure 2-3. The numbers in the figure are arranged
in blocks according to the first digit, The type of equipment or feature to which
they are assigned is shown in the block.