Regular Expression for the System-Supplied US Dial Plan

The regular expression specified for the US dial plan is shown below with annotations.

Following is a description of what this regular expression specifies.

Procedure

Step 1

The first digit must be 1.

Step 2

Three digits 0-9 must follow.

{3} means "3 of the preceding"

Step 3

One digit 2-9 must follow.

Step 4

Six digits 0-9 must follow.

{6} means "6 of the preceding"

Step 5

Zero or one of the following sequence can follow: between one and ten commas, followed by one or more digits 0-9.

{1,10} means "1 to 10 of the preceding"

+ means "one or more of the preceding"

{0,1} means "0 or 1 of the preceding"