Phone Numbers

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What do the numbers in a phone number do?

The telephone number that you dial to call somebody is an address, similar to the street address of your home. In the United States , all phone numbers have a total of 10 digits. The numbering plan was developed by AT&T in 1947. It uses three blocks of numbers - two blocks of three digits and a single block of four digits. It is used for wireline, phones at home, and cell phones.
 

Area code – A different area code is assigned to each specific geographic region in the United States , such as a city or a part of a state. In the example above, the geographic region “301” is part of Maryland . Area codes are assigned by the US Government.

Prefix – The first 3 digits of what you think of as your phone number are called the prefix. This prefix originally referred to the specific telephone company switch that a phone line connected to. Each switch at a phone company's central office had a special three-digit number.

Line number – The last four digits of your phone number is called the line number. It is the number assigned to the phone line that runs into your home or a business. The line number is assigned to the phone line and not to the phone you are using. Because the phone number is not assigned to the phone, the phone can be changed and you can even add more phones to the same line.

Click here to learn more about the history of the telephone.

Information for this web site was taken from the FCC site.