Lucent Technologies MERLIN LEGEND Release 6.1 System Manager's Manual page 411

MERLIN LEGEND Communications System Release 6.1
System Manager's Guide 555-661-118
B About Telecommunications
Signaling
Subsequently, 3-digit area codes were introduced to specify the area of the
country to be reached, and country codes were introduced for international
dialing. Finally, the individual telephone numbers expanded to the 7-digit numbers
in use today: a 3-digit central office code and a 4-digit extension number.
NOTE:
In the past, the North American Numbering Plan has used area codes that
have only a 0 or 1 for the middle digit, for example, 908 or 215. Currently,
the numbering plan is being changed so that any number (0 through 9) can
be used for the middle digit. This system has already been designed to
take that change into account.
Various standardized numbers have also been created for special services, for
example, area code 800 for toll-free service, and 911 for emergency service.
A special numbering plan is also used within the MERLIN LEGEND
Communications System to identify individual telephones, adjuncts (for example,
fax machines), trunks, and other features and aspects of the system. Depending
on the number of extensions and the needs of your company, you can choose
from three different numbering plans that allow 2-digit numbers, 3-digit numbers,
or customizable variable-length numbers, respectively.
Issue 1
August 1998
Page B-10