what is Numbering Plan? PSTN Dial Plan

Numbering plans are the fundamental for routing the voice calls through PSTN metric. The numbering plans areused to routing different voice calls with different numbering plans. ITU-T E.164 standard is used for creating different numbering plan in USA.North American Numbering Plan (NANP) is also known as “1+10” and is consist of following format.

NXX-NXX-XXXX

Where N is representing any number between 2 and 9, whereas X is any number between 0 to 9.

First three numbers NXX are area code, second three numbers NXX are representing prefix for region and final four digits XXXX are called Line number LN.

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