What Do Phone Number Digits Mean?

What Do Phone Number Digits Mean?
London, England, United Kingdom

What exactly are the numbers in a phone number—something you probably never consider—? The simplest explanation is that the numbers are essentially an address, much like a computer’s IP address. The number of digits in the phone number varies by country; in small towns, it may only have five or six; in large cities, it may have ten or more.

Phone numbers in the US are fixed-length and contain a total of 10 digits. The North American Numbering Plan (NANP), created by AT&T in the late 1940s to streamline the dialing of calls, primarily long-distance calls, is responsible for this. The strategy was implemented in 1951. A three-digit area code and a seven-digit local number make up the 10 digits of NANP numbers. Typically, the format is written as NXX-NXX-XXXX

  • Area codes, which are governed by the Federal Communications Commission (FCC), identify certain geographic areas, such as cities or portions of states. The 86 original area codes from 1947 still exist today. 
  • Prefix: Originally, the prefix related to the particular switch to which a phone line was attached. At a phone carrier’s central office, every switch had a distinct three-digit number. Since the introduction of automated switches, systems now provide the portability of local numbers (LNP). Today, a customer’s location—down to the city—is indicated via the prefix.
  • This is the number of the phone line you are dialing or the line number. You may easily switch phones or add extra phones to the same line because these numbers are assigned to the line rather than the phone directly.

Consider the three components as a street address, where the area code represents the city, the prefix signifies the street, and the line number represents the house.

Of course, you have to dial the international access code (011) before the country code when you contact another country. Calls from the United States can be placed to Canada and the majority of Caribbean countries without first dialing 011. Some nations have city codes as well as country codes, which you dial after the country code but before the local number.

Recognizing area codes

There are so many area codes in the U.S., as seen in this map of just the Northeast.

There are currently more than 325 area codes active in the US. Though some are not, most are given a particular geographic region. Most area codes, 36, are being used in California.

Blocks of 10,000 phone numbers were given to a single phone carrier in a certain area when the phone format first entered into use in the 1940s. For both small and large communities, that was usually an adequate amount. However, there was a great need for new phone numbers in the 1990s as cell phones suddenly became popular. The demand for more numbers and new area codes expanded with the growth of the internet, voice-over IP (VOIP), and cable companies.

For many years, adding a new area code involved dividing the existing area code into several regions. The majority of people had their phone numbers changed to the new area code, while those who lived elsewhere kept their old area code.

Overlay area codes increase the number of phone numbers that are available to the same geographic area as the original area code rather than dividing it into more regions. People were forced to switch to 10-digit dialing after overlay was introduced, even for local calls.

Therefore, the original area code for Georgia, dating back to 1947, was 404. Since then, several area codes have been added to the Atlanta region alone to accommodate new phone numbers, including 770, 678, and 470. The newest overlay area code for metro Atlanta, 943, was approved in March 2022 by the Georgia Public Service Commission. There won’t be any new 943 area code phone numbers assigned until carriers run out of numbers for the current codes.

Today, overlay codes are added to all new area codes. There are no longer any American cities where a call may be placed by simply dialing a seven-digit number. After the FCC selected 988 as the three-digit number for the National Suicide Prevention Lifeline, that came to an end on May 14, 2022. (similar to how dialing 911 from anywhere calls emergency services). 82 area codes in 35 states using the 988 local exchange had to switch to 10-digit dialing for all calls as a result.

Calls to 988 will be forwarded to the National Suicide Prevention Lifeline beginning on July 16, 2022.