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