Telephony is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties.
telephonydigital telephonytelephonetelephonicdigitalvoicetelephone systemdigital telephonephonetelephone service

Voice over IP

VoIPvoice over IPvoice over Internet Protocol
In this context the technology is specifically referred to as Internet telephony, or voice over Internet Protocol (VoIP).
The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of the analog voice signals, and encoding.

Local loop

local loopsubscriber linesubscriber loop
Each telephone was connected to the exchange via one wire pair, the local loop.
In telephony, the local loop (also referred to as a local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the common carrier or telecommunications service provider's network.

Public switched telephone network

public switched telephone networkPSTNtelephone network
Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the public switched telephone network (PSTN).
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.

Pulse-code modulation

PCMpulse-code modulationLPCM
End-to-end analog telephone networks were first modified in the early 1960s by upgrading transmission networks with Digital Signal 1 (DS1/T1) carrier systems, designed to support the basic 3 kHz voice channel by sampling the bandwidth-limited analog voice signal and encoding using PCM.
It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications.

Signalling System No. 7

SS7SS7 networkCCS7
Signaling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down most of the world's public switched telephone network (PSTN) telephone calls.


Companding is employed in telephony and other audio applications such as professional wireless microphones and analog recording.

Mobile phone

mobile phonecell phonemobile
In addition to replacing plain old telephone service (POTS), IP telephony services compete with mobile phone services by offering free or lower cost connections via WiFi hotspots.
In addition to telephony, 2000s-era mobile phones support a variety of other services, such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, video games, and digital photography.

Digital subscriber line

DSLdigital subscriber linexDSL
After the middle of the 20th century, fax and data became important secondary users of the network created to carry voices, and late in the century, parts of the network were upgraded with ISDN and DSL to improve handling of such traffic.
A naked DSL (also known as standalone or dry loop DSL) is a way of providing DSL services without a PSTN (analogue telephony) service.


videoconferencingvideo conferencingvideo chat
Video telephony restores such interactions to varying degrees.
This was first embodied in the device which came to be known as the video telephone, or videophone, and it evolved from intensive research and experimentation in several telecommunication fields, notably electrical telegraphy, telephony, radio, and television.

Speech coding

speech codingspeech codecspeech encoding
From this point of view, the A-law and μ-law algorithms (G.711) used in traditional PCM digital telephony can be seen as an earlier precursor of speech encoding, requiring only 8 bits per sample but giving effectively 12 bits of resolution.


Although analog carrier systems existed that multiplexed multiple analog voice channels onto a single transmission medium, digital transmission allowed lower cost and more channels multiplexed on the transmission medium.
In telephony, a customer's telephone line now typically ends at the remote concentrator box, where it is multiplexed along with other telephone lines for that neighborhood or other similar area.


The history of telephony is intimately linked to the invention and development of the telephone.
With the development of electronic switching systems in the 1960s, telephony gradually evolved towards digital telephony which improved the capacity, quality, and cost of the network.

Disruptive innovation

disruptive innovationdisruptive technologydisruptive technologies
VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone infrastructure technologies.

Computer network

computer networknetworknetworking
A specialization of digital telephony, Internet Protocol (IP) telephony involves the application of digital networking technology that was the foundation to the Internet to create, transmit, and receive telecommunications sessions over computer networks.
Examples of end-to-end encryption include HTTPS for web traffic, PGP for email, OTR for instant messaging, ZRTP for telephony, and TETRA for radio.

Timeline of the telephone

existence of a transatlantic telephonechronicles the developmenton-or-off transmission methods
This timeline of the telephone covers landline, radio, and cellular telephony technologies and provides many important dates in the history of the telephone.

Quality of service

quality of serviceQoSquality-of-service
Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network.

List of Australian AM radio stations

AM broadcaster
In the 1920s transmission on the medium wave band was dominated by amateurs who after qualifying by means of an examination and displaying proficiency in Morse code communication (though the band was restricted to telephony), were issued with a call sign consisting of a number denoting for which State the licence was issued (2=NSW, 3=Vic; 4=Qld; 5=SA and NT; 6=WA; 7=Tas) and a two-letter suffix of their own choosing.

Robotic voice effects

robotic voice effectsvocoder vocalsvoice shifting devices
The vocoder was originally designed to aid in the transmission of voices over telephony systems.

Vodafone Italy

VodafoneVodafone ItaliaVodafone Italia S.p.A.
Vodafone Italia S.p.A. (former Omnitel Pronto-Italia and Vodafone-Omnitel N.V. now branded Vodafone Italia) is an Italian telephony company, which has approximately 26,000,000 mobile customers with a market share of 29,5% (placing itself just behind TIM) and 2,300,000 customers on fixed lines with a market share of 10,2% (behind Telecom Italia and Infostrada).

Number pooling

number pooling
Number pooling is a method of reallocating telephony numbering space in the North American Numbering Plan, primarily in growth areas in the United States.

Computer Consoles Inc.

CCIPower 6/32CCI Power 6/32 “Tahoe”
Computer Consoles Inc. or CCI was a telephony and computer company located in Rochester, New York, United States, which did business first as a private, and then ultimately a public company from 1968 to 1990.

Google Voice

Google VoiceGrand Central
Google Voice is a telephony service that provides call forwarding and voicemail services, voice and text messaging, as well as U.S. and international call termination for Google Account customers in the U.S. and Canada.

Non-dialable point

non-dialable pointToll Stationnon-dialable toll point
In conventional landline telephony, a non-dialable toll point or toll station was a lone station or line serving a rural subscriber many miles from the nearest central office.

Echo suppression and cancellation

echo cancellationecho cancellerecho suppressor
Echo suppression and echo cancellation are methods used in telephony to improve voice quality by preventing echo from being created or removing it after it is already present.

Dial tone

dial tonedial-tonestutter dial tone
A dial tone is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected.