North American Numbering Plan

Area codeArea codesArea code(s)
The NANP divides the territories of its members into numbering plan areas (NPAs) which are encoded numerically with a three-digit telephone number prefix, commonly called the area code. Each telephone is assigned a seven-digit telephone number unique only within its respective plan area. The telephone number consists of a three-digit central office code and a four-digit station number. The combination of an area code and the telephone number serves as a destination routing address in the public switched telephone network (PSTN). For international call routing, the NANP has been assigned the international calling code 1 by the International Telecommunications Union (ITU).

Telephone number

phone numbertelephone numbersphone numbers
A telephone number is a sequence of digits assigned to a fixed-line telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network (PSTN) or other public and private networks. A telephone number serves as an address for switching telephone calls using a system of destination code routing. Telephone numbers are entered or dialed by a calling party on the originating telephone set, which transmits the sequence of digits in the process of signaling to a telephone exchange.

Voice over IP

VoIPVoice over Internet Protocolvoice-over-IP
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone service (POTS).

Telephone call

callphone callphone calls
Preceding, during, and after a traditional telephone call is placed, certain tones signify the progress and status of the telephone call: Cell phones generally do not use dial tones, because the technology used to transmit the dialed number is different from a landline. Unsolicited telephone calls are a modern nuisance. Common kinds of unwanted calls include prank calls, telemarketing calls, and obscene phone calls. Caller ID provides some protection against unwanted calls, but can still be turned off by the calling party.

Telephone exchange

exchangescentral officeexchange
All central offices within a larger region, typically aggregated by state, were assigned a common numbering plan area code. With the development of international and transoceanic telephone trunks, especially driven by direct customer dialing, similar efforts of systematic organization of the telephone networks occurred in many countries in the mid-20th century. For corporate or enterprise use, a private telephone exchange is often referred to as a private branch exchange (PBX), when it has connections to the public switched telephone network.

Signalling System No. 7

SS7Signaling System 7Signalling System 7
'''Signaling System No. 7 (SS7''') is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down telephone calls in most parts of the world-wide public switched telephone network (PSTN). The protocol also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other services. In North America SS7 is often referred to as Common Channel Signaling System 7 (CCSS7). In the United Kingdom, it is called C7 (CCITT number 7), number 7 and Common Channel Interoffice Signaling 7 (CCIS7). In Germany, it is often called Zentraler Zeichengabekanal Nummer 7 (ZZK-7).


phonetelephonesLocal Telephone Service
These exchanges were soon connected together, eventually forming an automated, worldwide public switched telephone network. For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973. In later decades their analog cellular system evolved into digital networks with greater capability and lower cost. Convergence has given most modern cell phones capabilities far beyond simple voice conversation. Most are smartphones, integrating all mobile communication and many computing needs.

Emergency telephone number

emergency callemergency numberemergency calls
In many countries the public switched telephone network has a single emergency telephone number (sometimes known as the universal emergency telephone number or the emergency services number) that allows a caller to contact local emergency services for assistance. The emergency number differs from country to country; it is typically a three-digit number so that it can be easily remembered and dialed quickly. Some countries have a different emergency number for each of the different emergency services; these often differ only by the last digit. See List of emergency telephone numbers. The emergency telephone number is a special case in the country's telephone number plan.

VoIP phone

IP phoneSIP phoneIP Phones
A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet, instead of the traditional public switched telephone network (PSTN). Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols. VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone. Traditional PSTN phones are used as VoIP phones with analog telephone adapters (ATA).

Overlay plan

overlayoverlaidoverlay area code
Service-specific overlay: the first overlay area code in the NANPA, 917, is the only example of this; it was established originally as an area code specifically for cellphones and pagers in New York City, but soon afterward, the FCC said that area codes going forth could not be service-specific, but it allowed 917 to remain as such. However, 917 is now used for landlines in New York City on a limited basis. List of area code overlays. Interexchange carrier. Telephone exchange. Telephone numbering plan. Exhaust date. FCC FAQ - Carrier Identification Codes (CICs) and Seven-Digit Carrier Access Code (CAC) Dialing.

Toll-free telephone number

toll-freetoll-free number800 number
A toll-free telephone number or freephone number is a telephone number that is billed for all arriving calls instead of incurring charges to the originating telephone subscriber. For the calling party, a call to a toll-free number from a landline is free of charge. A toll-free, Freecall, Freephone, 800, 0800 or 1800 number is identified by a dialing prefix similar to a geographic area code, such as 909 (the area code that covers eastern Los Angeles County and southwestern San Bernardino County). The specific service access numbers vary by country.


Fixed linefixed-lineland line
That same year, 2008, about 77% of adults owned a mobile phone. In the year 2013, 91% of adults in the United States owned a mobile phone. Almost 60% of those with a mobile had a smartphone. A National Health Interview Survey of 19,956 households by the Centers for Disease Control and Prevention released May 4, 2017 showed only 45.9 percent of U.S. households still had landlines, while 50.8 percent had only cell phones. Over 39 percent had both. In Canada, more than one in five of households use cell phones as their only source for telephone service. In 2013, statistics showed that 21% of households claimed to only use cellular phones.

Caller ID

caller line identificationCaller-IDCalling Line Identification
In the typical telephony environment, a PBX connects to the local service provider through Primary Rate Interface (PRI) trunks. Generally, although not absolutely, the service provider simply passes whatever calling line ID appears on those PRI access trunks transparently across the Public Switched Telephone Network (PSTN). This opens up the opportunity for the PBX administrator to program whatever number they choose in their external phone number fields. Some IP phone services (ITSPs, or Internet Telephony Service Providers) support PSTN gateway installations throughout the world. These gateways egress calls to the local calling area, thus avoiding long distance toll charges.

Directory assistance

directory enquiries118 5001-800-555-1212
Example: The caller is looking for a listing in Los Angeles, CA (area code 213) and dials 213-555-1212. In this case Verizon bills the call. 4) 00 and ask for the international directory assistance operator. AT&T provides International Directory Assistance calls. See for additional information and country and city codes. 555 (telephone number). Telephone directory.


The wireless revolution began in the 1990s, with the advent of digital wireless networks leading to a social revolution, and a paradigm shift from wired to wireless technology, including the proliferation of commercial wireless technologies such as cell phones, mobile telephony, pagers, wireless computer networks, cellular networks, the wireless Internet, and laptop and handheld computers with wireless connections. The wireless revolution has been driven by advances in radio frequency (RF) and microwave engineering, and the transition from analog to digital RF technology.


STIR/SHAKEN, or SHAKEN/STIR, is a suite of protocols and procedures intended to combat caller ID spoofing on public telephone networks. Caller ID spoofing is used by robocallers to mask their identity or to make it appear the call is from a legitimate source, often a nearby phone number with the same area code and exchange, or from well-known agencies like the Internal Revenue Service or Ontario Provincial Police. This sort of spoofing is common for calls originating from voice-over-IP (VOIP) systems, which can be located anywhere in the world. STIR, short for Secure Telephony Identity Revisited, is being defined by a Working Group of the Internet Engineering Task Force.


Short Message Servicetext messagetext messages
The first action plan of the CEPT Group GSM was approved in December 1982, requesting that "The services and facilities offered in the public switched telephone networks and public data networks ... should be available in the mobile system." This plan included the exchange of text messages either directly between mobile stations, or transmitted via message handling systems in use at that time. The SMS concept was developed in the Franco-German GSM cooperation in 1984 by Friedhelm Hillebrand and Bernard Ghillebaert. The GSM is optimized for telephony, since this was identified as its main application.

Telephone tapping

To the mobile phones in its vicinity, a device called an "IMSI-catcher" pretends to be a legitimate base station of the mobile phone network, thus subjecting the communication between the phone and the network to a man-in-the-middle attack. This is possible because, while the mobile phone has to authenticate itself to the mobile telephone network, the network does not authenticate itself to the phone.

Vertical service code

calling featureservice featureCustom Local Area Signaling Services
Public switched telephone network. Short code. Signalling System 7.


911911 call9-1-1 call
Depending on the mobile phone hardware, one of two types of location information can be provided to the operator. The first is Wireless Phase One (WPH1), which is the tower location and the direction the call came from, and the second is Wireless Phase Two (WPH2), which provides an estimated GPS location. As Voice over Internet Protocol (VoIP) technology matured, service providers began to interconnect VoIP with the public switched telephone network and marketed the VoIP service as a cheap replacement phone service.

UK telephone code misconceptions

common misconceptionerroneous UK telephone codesmisquoted
Although the problem is most prevalent in London, similar misconceptions also affect other area codes which were created as a result of PhONEday and the Big Number Change. The inconvenience of the possible misconceptions subsequently became more significant and apparent, for example in Bristol with the issuing of new numbers within the 0117 code area where initially all numbers were revised such that their local 7-digit string began with 9. From 1997 new numbers began to be issued whose local 7-digit string began with a number other than 9, starting with 3xx-xxxx: The United Kingdom adopts an open dialling plan for area codes within its public switched telephone network.


Nortel NetworksNorthern TelecomNorthern Electric
It served both general businesses and communications carriers (landline telephone, mobile phone, and cable TV carriers). Technologies included telephonic (voice) equipment, fiber optics, local wireless, and multimedia. Past products included: In 2016 the Canadian Broadcasting Corporation, reported that lawyers and accountants received $2.5 billion from Nortel's estate In September 1991, Julian Assange was discovered in the act of hacking into the Melbourne master terminal of Nortel. In 2012, The Wall Street Journal reported that in 2004, Nortel discovered that crackers gained almost-complete access to Nortel's systems.

Wireless home phone

A wireless home phone service is a service that allows a regular wired telephone to connect to a cellular network, as if it were a mobile phone. It is an example of a wireless last mile connection to the public switched telephone network, also known as a wireless local loop. A small device, about the size of a home wireless router, contains the necessary electronics which allow plain old telephone service to be provided to one or two telephone jacks on the back of the unit, as well as having a small radio antenna and a transceiver for the wireless side of the connection. LED indicator lights on the front typically show signal strength and voicemail messages waiting.

Timeline of the telephone

chronicles the developmentexistence of a transatlantic telephoneon-or-off transmission methods
Hodges develop the silicon-gate CMOS (complementary MOS) pulse-code modulation (PCM) codec-filter chip, which has since been the industry standard for digital telephony, widely used in the public switched telephone network (PSTN) as well as cordless telephones and cell phones. 1981: The world's first fully automatic mobile phone system NMT is started in Sweden and Norway. 1981: BT introduces the British Telephone Sockets system. 1982: FCC approved AT&T proposal for AMPS and allocated frequencies in the 824-894 MHz band. 1982: Caller ID patented by Carolyn Doughty, Bell Labs. 1983: last manual telephone switchboard in Maine is retired. 1984: AT&T completes the divestiture of its local operating

Index of telephone-related articles

Mobile phone. Philipp Reis. Plain old telephone service (POTS). Private branch exchange. Public switched telephone network. Ringaround. Satellite phone. Sidetone. Telecommunications. Telephone. Telephone call. Telephone directory. Telephone exchange. Telephone line. Telephone newspaper. Telephone number. Telephone switchboard. Telephone tapping. Telephony. Thomas Edison. Timeline of the telephone. Tip and ring (Wiring terminology). Toll-free telephone number.