Voice over IP

VoIPvoice over Internet Protocolvoice-over-IP
Voice over Internet Protocol (VoIP), also called IP telephony, is a methodology 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).

Telephone number

phone numbertelephone numbersphone numbers
Local number portability (LNP) allows a subscriber to request moving an existing telephone number to another telephone service provider. Number portability usually has geographic limitations, such as an existing local phone company only being able to port to a competitor within the same rate centre. Mobile carriers may have much larger market areas, and can assign or accept numbers from any area within the region. In many telephone administrations, cell phone telephone numbers are in organized in prefix ranges distinct from land line service, which simplifies mobile number portability, even between carriers.

North American Numbering Plan

Area codeArea codesArea code(s)
Initially, the area code 917 for New York City was specifically assigned for this purpose within the boroughs; however, a Federal court overturned the practice and the use of an area code for a specific telephony purpose. Since mobile telephony has been expanding faster than landline use, new area codes typically have a disproportionately large fraction of mobile and nomadic numbers, although landline and other services rapidly follow and local network portability can blur these distinctions. The experience of Hurricane Katrina and similar events revealed a possible disadvantage of the methods employed in the geographic assignment of cellular numbers.

Telephone tapping

Mobile phones have numerous privacy issues. Governments, law enforcement and intelligence services use mobiles to perform surveillance in the UK and the US. They possess technology to activate the microphones in cell phones remotely in order to listen to conversations that take place near to the person who holds the phone. Mobile phones are also commonly used to collect location data.

Public switched telephone network

PSTNtelephone networkpublic telephone network
The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication. The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other.

Telephone exchange

exchangescentral officeexchange
In the United States and Canada, the Bell System established in the 1940s a uniform system of identifying central offices with a three-digit central office code, that was used as a prefix to subscriber telephone numbers. 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.

Signalling System No. 7

SS7SS7 NetworkCCS7
Telephone User Part (TUP) is a link-by-link signaling system used to connect calls. ISUP is the key user part, providing a circuit-based protocol to establish, maintain, and end the connections for calls. Transaction Capabilities Application Part (TCAP) is used to create database queries and invoke advanced network functionality, or links to Intelligent Network Application Part (INAP) for intelligent networks, or Mobile Application Part (MAP) for mobile services. Several SS7 vulnerabilities that allow cell phone users to be secretly tracked were publicized in 2008.


smartphonessmart phonesmart phones
Smartphones (contraction of smart and telephone) are a class of mobile phones and of multi-purpose mobile computing devices. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, which facilitate wider software, internet (including web browsing over mobile broadband), and multimedia functionality (including music, video, cameras, and gaming), alongside core phone functions such as voice calls and text messaging.


GSM (850/900/1800/1900) GSM/GPRS/EDGEGSM technology
International Mobile Subscriber Identity (IMSI). Long Term Evolution (LTE). MSISDN Mobile Subscriber ISDN Number. Nordic Mobile Telephone (NMT). ORFS. Personal communications network (PCN). RTP audio video profile. Simulation of GSM networks. Standards. Comparison of mobile phone standards. GEO-Mobile Radio Interface. GSM 02.07 - Cellphone features. GSM 03.48 – Security mechanisms for the SIM application toolkit. Intelligent Network. Parlay X. RRLP – Radio Resource Location Protocol. Um interface. Visitors Location Register (VLR). GSM Association—Official industry trade group representing GSM network operators worldwide. 3GPP—3G GSM standards development group.

Overlay plan

overlayoverlaidoverlay area code
It was originally established as an area code specifically for cell phones and pagers in New York City, but soon after, the FCC said area codes going forth could not be service-specific, but they allowed 917 to remain as such. However, 917 is being 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.

Toll-free telephone number

toll-freetoll-free number800 number
Countries around the world use various dialing prefixes to denote toll-free services in their telephone networks. Toll-free numbers in the North American Numbering Plan (NANP) are commonly called "800 numbers" after the original area code which was used to dial them. They include the area code 800 (since January 1, 1966), 888 (since March 1, 1996), 877 (since April 4, 1998), 866 (since July 29, 2000), 855 (since October 9, 2010), 844 (since December 7, 2013), and 833 (since April 22, 2017). Area codes reserved for future expansion include 822, 880 through 887, and 889. The original Wide Area Telephone Service is obsolete.


As of 2009, out of Japan's $20 billion gaming market, $6 billion of that amount is generated from arcades, which represent the largest sector of the Japanese video game market, followed by home console games and mobile games at $3.5 billion and $2 billion, respectively. In the present day, Japan is the world's largest market for mobile games. The country's traditional console gaming market itself is today largely dominated by handheld game consoles rather than home consoles. In 2014, Japan's consumer video game market grossed $9.6 billion, with $5.8 billion coming from mobile gaming.

555 (telephone number)

555555 telephone number5-5-5
God's number was changed to a 555 exchange prefix in the video release of the movie. "777-9311" by The Time used Dez Dickerson's actual telephone number at the time the song was written, causing his phone to ring off the hook until he had his number changed. The Alicia Keys song "Diary" contains a real number in New York's area code 347, an overlay, but does not indicate an area code; the same number in some other area code is a common misdial.

Caller ID spoofing

spoofspoofeda false origin is displayed
The name provided by the caller (in the analog telephone adapter configuration screen for voice-over-IP users or on the web interface on a spoofing provider) is blindly passed verbatim to the called party and may be spoofed at will. The name is generated from a telephone company database using the spoofed caller ID number. A destination provider may display no name or just the geographic location of the provided telephone area code on caller ID (e.g., "ARIZONA", "CALIFORNIA", "OREGON", or "ONTARIO"). This often occurs where the destination carrier is a low-cost service (such as a VoIP provider) running no database or outdated data in which the number is not found.


As of 2015, the landline telephones in most residential homes are analog—that is, the speaker's voice directly determines the signal's voltage. Although short-distance calls may be handled from end-to-end as analog signals, increasingly telephone service providers are transparently converting the signals to digital signals for transmission. The advantage of this is that digitized voice data can travel side-by-side with data from the Internet and can be perfectly reproduced in long distance communication (as opposed to analog signals that are inevitably impacted by noise). Mobile phones have had a significant impact on telephone networks.

Verizon Communications

VerizonBell AtlanticGTE
*List of United States telephone companies The Bell Telephone Company of Pennsylvania. New Jersey Bell. Diamond State Telephone. C&P Telephone (itself comprising four subsidiaries).

Vertical service code

calling featureservice featureCLASS
A vertical service code (VSC) is a sequence of digits and the signals star and number sign dialed on a telephone keypad or rotary dial to enable or disable certain telephony service features. Some vertical service codes require dialing of a telephone number after the code sequence. On a touch tone telephone, the codes are usually initiated with the star key, resulting in the commonly used name star codes. On rotary dial telephones, the star is replaced by dialing 11. In North American telephony, VSCs were developed by AT&T Corp. as Custom Local Area Signaling Services (CLASS or LASS) codes in the 1960s and 70s.


iPhonesiPhone appApple iPhone
Additionally, the program is limited to just the iPhone hardware; cell phone service from a network operator is not included. Before the release of the iPhone, handset manufacturers such as Nokia and Motorola were enjoying record sales of cell phones based more on fashion and brand rather than technological innovation. The smartphone market, dominated at the time by BlackBerry OS and Windows Mobile devices, was a "staid, corporate-led smartphone paradigm" focused on enterprise needs. Phones at the time were designed around carrier and business limits which were conservative with regards to bandwidth usage and battery life.

UK telephone code misconceptions

common misconceptionerroneous UK telephone codesmisquoted
Telephone numbering plan.