Dial plan

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A dial plan establishes the expected number and pattern of digits for a telephone number. This includes country codes, access codes, area codes and all combinations of digits dialed. For instance, the North American public switched telephone network (PSTN) uses a 10-digit dial plan that includes a 3-digit area code and a 7-digit telephone number. Most PBXs support variable-length dial plans that use 3 to 11 digits. Dial plans must comply with the telephone networks to which they connect.

In the U.S., some typical dial plans include:

  • Internal extension numbers of two, three, or four digits.
  • Local numbers of seven or ten digits, which may be preceded by a 9 if required to access an outside line.
  • Long distance numbers of eleven digits, consisting of a 1, then a three-digit area code, then a seven-digit number; Preceded by a 9 if required.
  • International numbers of any length starting with 011 and preceded by a 9 if required

[edit] Syntax

The following syntax used to identify a dial plan in a digit map is adapted from [RFC 2705].

Dial Plan Syntax 
To specify a 

Enter the following

Result
Digit
0 1 2 3 4 5 6 7 8 9 *
 Identifies a specific digit (do not use #)
Range
[digit-digit]
 Identifies any digit dialed that is included in the range
Range
[digit-digit, digit]
 Specifies a range as a comma separated list
Wildcard
x
 x matches any single digit that is dialed
Wildcard
.
 . matches an arbitrary number of digits
Timer
T
 Indicates that an additional time out period of 4 seconds should take place before automatic dialing starts

Some dial plan examples using the above syntax look as follows:

Dial Plan Syntax Examples 
For calls to

Users dial

Dial plan
Internal Extension
a two digit number
 xx
Local Number
9 (if required for an outside line) and then a seven digit number
 9xxxxxxxT
Emergency
911
 911
Local Operators
9 (if required for an outside line) then 0
 90T
Long Distance
9 (if required), 1, area code and local number
 91xxxxxxxxxx
International
9 (if required), 011, any number of additional digits
 9011x.T

[edit] See also

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