NANP (institutions given the phone number) started back in 1947 in the United States and Canada, who soon joined with several countries and regions. Under the NANP, each number consisting of 3-area number (NPA), and the local number number 7.
Initially, there were 86 area codes, even though Hawaii, Alaska, and the Caribbean is still part of the NANP. Today, there are nearly 300 area code.
At first, the number of local area code and known to exercise caution range of numbers. Rule said that both the local area code is not allowed to start with 0 or 1. Your local second number is 0 or 1. In this way, only to watch the first 3 digits of the numbers, one can know whether it is local or long distance calls.
As time passed, many area codes are adjusted or split so that each region will have a sufficient number of needs. More phone lines are needed to increase the population and economic growth, major technological developments (such as DID PBX, which enables call in directly, not through the reception) as fax, modem, cellular respiration, Pa., and singer.
The 1970s brought a new plan to manage the needs of increasing numbers. The first step is to allow the second number of the local population is 0 or 1 - particularly in areas such as the high density of New York and New York, but all the capital in other areas as well. The second step he took effect in 1995, when the area code can have a number between and including 0 and 9 as the second number. Second attempt to increase the number of NANP numbers five times more.
