Business telephone system

PBXprivate branch exchangePABX
A private branch exchange (PBX) is a telephone exchange or switching system that serves a private organization and permits sharing of central office trunks between internally installed telephones, and provides intercommunication between those internal telephones within the organization without the use of external lines. The central office lines provide connections to the public switched telephone network (PSTN) and the concentration aspect of a PBX permits the shared use of these lines between all stations in the organization. Its intercommunication ability allows two or more stations to directly connect while not using the public switched telephone network.

E.164 is an international standard (ITU-T Recommendation), titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks. E.164 defines a general format for international telephone numbers. Plan-conforming numbers are limited to a maximum of 15 digits, excluding the international call prefix. The presentation of a number at the B-party device is usually prefixed with the plus sign, indicating that the number includes the country calling code.

Pulse-code modulation

By the 1990s, telecommunication networks such as the public switched telephone network (PSTN) had been largely digitized with very-large-scale integration (VLSI) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges, user-end modems and a wide range of digital transmission applications such as the integrated services digital network (ISDN), cordless telephones and cell phones. PCM is the method of encoding typically used for uncompressed digital audio. In the diagram, a sine wave (red curve) is sampled and quantized for PCM. The sine wave is sampled at regular intervals, shown as vertical lines.

Integrated Services Digital Network

ISDN is also used as a smart-network technology intended to add new services to the public switched telephone network (PSTN) by giving users direct access to end-to-end circuit-switched digital services and as a backup or failsafe circuit solution for critical use data circuits. ISDN is used heavily by the broadcast industry as a reliable way of switching low-latency, high-quality, long-distance audio circuits.


867-5309867-5309 (Jenny)867-5309 and asking for Jenny
In July 2009, Jason Kaplan had the number assigned to a Vonage phone line in the name of a small business in area code 267 and then listed the entire business for sale on eBay. The auction closed at $5,500. In January 2013, Five309 LLC announced plans to use 855-867-5309 and 888-867-5309 to promote website In 2013, the number was still ringing up fifty misdialled calls daily for Florida realtor Carrie Routt in area code 850. Fort Collins, Colorado restaurant, Totally 80's Pizza, uses this number as part of its 1980s theme, in area code 970. Fictitious telephone number. Denial-of-service attack#Telephony denial-of-service.


Global System for Mobile CommunicationsGSM networkGSM (850/900/1800/1900)
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets. It was first deployed in Finland in December 1991. By the mid-2010s, it became a global standard for mobile communications achieving over 90% market share, and operating in over 193 countries and territories. 2G networks developed as a replacement for first generation (1G) analog cellular networks. The GSM standard originally described a digital, circuit-switched network optimized for full duplex voice telephony.

Wideband audio

HD VoicewidebandWideband Voice
Wideband audio, also known as wideband voice or HD voice, is high definition voice quality for telephony audio, contrasted with standard digital telephony "toll quality". It extends the frequency range of audio signals transmitted over telephone lines, resulting in higher quality speech. The range of the human voice extends from 80 Hz to 14 kHz but traditional, voiceband or narrowband telephone calls limit audio frequencies to the range of 300 Hz to 3.4 kHz. Wideband audio relaxes the bandwidth limitation and transmits in the audio frequency range of 50 Hz to 7 kHz or even up to 22 kHz.

Long-distance calling

long distancelong-distancelong distance call
Area code 700, rarely used, is reserved for carrier-specific services; each carrier places a recorded self-identification message on 1-700-555-4141 to allow a subscriber to identify the default InterLATA carrier for their line. Long-distance calls may be classified into two groups. Interstate long-distance or inter-LATA interstate long-distance, the most common group, is the one for which long-distance carriers are usually chosen by telephone customers. Another form of long-distance call, increasingly relevant to more U.S. states, is known as an inter-LATA intrastate long-distance call. This refers to a calling area outside of the customer’s LATA but within the customer's state.


SkypingSkype PreviewJosh Silverman
Caller ID spoofing. Censorship of Skype. Comparison of instant messaging clients. Comparison of instant messaging protocols. Comparison of VoIP software. List of video telecommunication services and product brands. Mobile VoIP. Presence information. Unified communications.

Sampling (signal processing)

sampling ratesamplingsample rate
For most phonemes, almost all of the energy is contained in the 100 Hz–4 kHz range, allowing a sampling rate of 8 kHz. This is the sampling rate used by nearly all telephony systems, which use the G.711 sampling and quantization specifications. Standard-definition television (SDTV) uses either 720 by 480 pixels (US NTSC 525-line) or 720 by 576 pixels (UK PAL 625-line) for the visible picture area. High-definition television (HDTV) uses 720p (progressive), 1080i (interlaced), and 1080p (progressive, also known as Full-HD). In digital video, the temporal sampling rate is defined the frame rate – or rather the field rate – rather than the notional pixel clock.

Touch-Tone Terrorists

Pete Dzoghi
It appeared under the name The Junkyard Willie Prank Call Tapes 4 due to its release shortly after the September 11 attacks. This CD features 22 prank calls. The Junkyard Willie Movie: Lost In Transit: A straight-to-DVD movie based loosely on the Touch-Tone Terrorists characters. The film, released in 2008, includes one new prank call. Customer Care Creeps: This is the 5th CD in the series, was released in two parts in 2009 and 2015 and contains 16 calls. Caller ID spoofing. Jerky Boys. The Wack Pack. Tube Bar prank calls. Touch-tone Terrorists official Web Site. Homepage of the lost in transit movie.

Fictitious telephone number

Drama usefictional numbersfictional telephone number
Per the ACMA web page – Fictitious numbers for radio, books, film & TV, version October 21, 2009: In Hungary, telephone numbers are in the format 06 + area code + subscriber number, where the area code is a single digit 1 for Budapest, the capital, followed by a seven digit subscriber number, and two digits followed by either seven (for cell phone numbers) or six digits (others). for other areas, cell phone numbers or non-geographic numbers like toll-free or premium-rate numbers. Two digit area codes which consist of digits between 2 and 9 are geographic areas, while area codes ending with a 0 or a 1 denote other services.

Mobile telephony

mobile communicationmobile telecommunicationsmobile communications
Mobile telephony is the provision of telephone services to phones which may move around freely rather than stay fixed in one location. Telephony is supposed to specifically point to a voice-only service or connection, though sometimes the line may blur. Mobile phones connect to a terrestrial cellular network of base stations (cell sites), whereas satellite phones connect to orbiting satellites. Both networks are interconnected to the public switched telephone network (PSTN) to allow any phone in the world to be dialed. In 2010 there were estimated to be five billion mobile cellular subscriptions in the world.

Analog signal

analoganalogueanalogue signal
An analog signal is any continuous signal for which the time-varying feature (variable) of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. For example, in an analog audio signal, the instantaneous voltage of the signal varies continuously with the pressure of the sound waves. It differs from a digital signal, in which the continuous quantity is a representation of a sequence of discrete values which can only take on one of a finite number of values.

Mobile radio telephone

0G0G mobilemanual mobile telephone system
The B-Netz launched 1972 in West Germany as the country's second public commercial mobile phone network (but the first one that did not require human operators to connect calls). Walkie-talkie. List of mobile phone generations. 1G. 2G. 3G. 4G. 5G. Mobile rig. Mobile Telephone Service - (A pre-cellular VHF radio system that linked to the PSTN). Radiotelephone - (A communications device for transmission of speech over radio). Satellite telephone. Mobile Phone History. Mobile Phone Generations. Evolution of Mobile Wireless Technology from 0G to 5G.

Nuisance call

telephone harassmentnuisance callsnuisance phone calls
However, these do not provide complete protection: harassers can use payphones and, in some cases, caller ID (but not necessarily automatic number identification itself) can be spoofed or blocked. Mobile telephone abusers can (at some cost) use "throwaway" mobile phones or SIMs. Voice over IP users may send bogus caller ID or route calls through servers in multiple countries. Even in these cases, with sufficient law enforcement and telco effort, persistent abusers can often be tracked down by technical means. Call screening is another countermeasure against unsolicited calls. Most telephone companies have a department devoted to handling complaints regarding unsolicited phone calls.


Japan (日本, Nippon or Nihon ; formally 日本国, or Nihon-koku, ) is an island country in East Asia. Located in the Pacific Ocean, it lies off the eastern coast of the Asian continent and stretches from the Sea of Okhotsk in the north to the East China Sea and the Philippine Sea in the south.


Most products use methods similar to those used to mitigate SPIT (spam over Internet telephony) and can be broadly categorised by the primary method used. However, due to the complexity of the problem, no single method is sufficiently reliable. Solutions are available as both hardware and software products. Mobile apps are especially prevalent as they use techniques which do not require the modification of infrastructure. Many products are limited to use only on a single medium, such as traditional copper landlines, or mobile phone contracts from a specific mobile phone operator.


videoconferencingvideo conferencingvideo chat
The widest deployment of video telephony now occurs in mobile phones. Nearly all mobile phones supporting UMTS networks can work as videophones using their internal cameras, and are able to make video calls wirelessly to other UMTS users in the same country or internationally. As of the second quarter of 2007, there are over 131 million UMTS users (and hence potential videophone users), on 134 networks in 59 countries. Mobile phones can also use broadband wireless Internet, whether through the cell phone network or over a local wifi connection, along with software-based videophone apps to make calls to any video-capable Internet user, whether mobile or fixed.

Denial-of-service attack

DDoSdenial of servicedistributed denial of service
Widespread publication of a number can also flood it with enough calls to render it unusable, as happened by accident in 1981 with multiple +1-area code-867-5309 subscribers inundated by hundreds of misdialed calls daily in response to the song 867-5309/Jenny. TDoS differs from other telephone harassment (such as prank calls and obscene phone calls) by the number of calls originated; by occupying lines continuously with repeated automated calls, the victim is prevented from making or receiving both routine and emergency telephone calls. Related exploits include SMS flooding attacks and black fax or fax loop transmission.

Digital audio

digital musicdigitalaudio
By the 1990s, telecommunication networks such as the public switched telephone network (PSTN) had been largely digitized with VLSI (very large-scale integration) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges, user-end modems and a range of digital transmission applications such as the integrated services digital network (ISDN), cordless telephones and cell phones. Digital audio is used in broadcasting of audio. Standard technologies include Digital audio broadcasting (DAB), Digital Radio Mondiale (DRM), HD Radio and In-band on-channel (IBOC).

Telephone company

telecommunications companytelephone companiestelco
Bell Telephone Company, forerunner of AT&T in the U.S. Internet telephony service provider. Competitive local exchange carrier (in Canada and the U.S.). Communications service provider. History of the telephone. Incumbent local exchange carrier (of the Bell System). List of telephone operating companies. List of mobile network operators. Mobile network operator. Plain old telephone service (POTS). Public switched telephone network. Telecommunications Industry Association (for the development of U.S. telecom standards). Regional Bell Operating Company (in the U.S.). Service provider. Telecommunications service provider. The Phone Company, free, non-commercial email-to-fax service.

The New York Times

New York TimesNY TimesNYT
The New York Times (sometimes abbreviated as the NYT and NYTimes) is an American newspaper based in New York City with worldwide influence and readership. Founded in 1851, the paper has won 127 Pulitzer Prizes, more than any other newspaper. The Times is ranked 18th in the world by circulation and 3rd in the U.S.

List of North American Numbering Plan area codes

List of NANP area codesList of North American area codesArea Codes
Area codes with the last two digits matching, such as 322 and 800, are considered easily recognizable codes (ERC), where the series of 8xx are used for toll-free services. Future area codes are written in italics. * Very small localities adjacent to the 60th parallel are served by exchanges within the 867 area code. A customs station in B.C. is served by an Alaska exchange. Bell System. List of country calling codes. List of future North American area codes. List of original NANP area codes. Telephone numbers in the Americas.