Telephony ( ) is the field of technology involving the development, application, and deployment of

telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is intimately linked to the invention and development of the

telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...

. Telephony is commonly referred to as the construction or operation of telephones and telephonic systems and as a system of telecommunications in which telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires. The term is also used frequently to refer to computer hardware, software, and computer network systems, that perform functions traditionally performed by telephone equipment. In this context the technology is specifically referred to as Internet telephony, or

voice over Internet Protocol 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 t ...

(VoIP).

Overview

The first telephones were connected directly in pairs. Each user had a separate telephone wired to each locations to be reached. This quickly became inconvenient and unmanageable when users wanted to communicate with more than a few people. The invention of the

telephone exchange A telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syst ...

provided the solution for establishing telephone connections with any other telephone in service in the local area. Each telephone was connected to the exchange at first with one wire, later one wire pair, the

local loop In telephony, the local loop (also referred to as the 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 commo ...

. Nearby exchanges in other service areas were connected with trunk lines, and long-distance service could be established by relaying the calls through multiple exchanges. Initially, exchange switchboards were manually operated by an attendant, commonly referred to as the " switchboard operator". When a customer cranked a handle on the telephone, it activated an indicator on the board in front of the operator, who would in response plug the operator headset into that jack and offer service. The caller had to ask for the called party by name, later by number, and the operator connected one end of a circuit into the called party jack to alert them. If the called station answered, the operator disconnected their headset and completed the station-to-station circuit. Trunk calls were made with the assistance of other operators at other exchangers in the network. Until the 1970s, most telephones were permanently wired to the telephone line installed at customer premises. Later, conversion to installation of jacks that terminated the

inside wiring On-premises wiring (customer premises wiring) is customer-owned telecommunication transmission (telecommunications), transmission or distribution lines. The transmission lines may be metallic (copper) or optical fiber, and may be installed withi ...

permitted simple exchange of telephone sets with telephone plugs and allowed portability of the set to multiple locations in the premises where jacks were installed. The inside wiring to all jacks was connected in one place to the wire drop which connects the building to a cable. Cables usually bring a large number of drop wires from all over a district

access network An access network is a type of telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to one another. The access network may be further ...

to one wire center or telephone exchange. When a telephone user wants to make a

telephone call A telephone call is a connection over a telephone network between the called party and the calling party. First telephone call The first telephone call was made on March 10, 1876, by Alexander Graham Bell. Bell demonstrated his ability to "ta ...

, equipment at the exchange examines the dialed

telephone number A telephone number is a sequence of digits assigned to a landline 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 f ...

and connects that

telephone line A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or ot ...

to another in the same wire center, or to a trunk to a distant exchange. Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the public switched telephone network (PSTN). In the second half of the 20th century, fax and data became important secondary applications of the network created to carry voices, and late in the century, parts of the network were upgraded with

ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work ...

and

DSL Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric dig ...

to improve handling of such traffic. Today, telephony uses digital technology (

digital telephony 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. The history of telephony is i ...

) in the provisioning of telephone services and systems. Telephone calls can be provided digitally, but may be restricted to cases in which the last mile is digital, or where the conversion between digital and analog signals takes place inside the telephone. This advancement has reduced costs in communication, and improved the quality of voice services. The first implementation of this,

, permitted all data transport from end-to-end speedily over telephone lines. This service was later made much less important due to the ability to provide digital services based on the

IP protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP h ...

. Since the advent of personal computer technology in the 1980s,

computer telephony integration Computer telephony integration, also called computer–telephone integration or CTI, is a common name for any technology that allows interactions on a telephone and a computer to be coordinated. The term is predominantly used to describe desktop- ...

(CTI) has progressively provided more sophisticated telephony services, initiated and controlled by the computer, such as making and receiving voice, fax, and data calls with

telephone directory A telephone directory, commonly called a telephone book, telephone address book, phonebook, or the white and yellow pages, is a listing of telephone subscribers in a geographical area or subscribers to services provided by the organization that ...

services and

caller identification Caller identification (Caller ID) is a telephone service, available in analog and digital telephone systems, including voice over IP (VoIP), that transmits a caller's telephone number to the called party's telephone equipment when the call is ...

. The integration of telephony software and computer systems is a major development in the evolution of office automation. The term is used in describing the computerized services of call centers, such as those that direct your phone call to the right department at a business you're calling. It's also sometimes used for the ability to use your personal computer to initiate and manage phone calls (in which case you can think of your computer as your personal call center).

Digital telephony

Digital telephony is the use of

digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usual ...

in the operation and provisioning of telephony systems and services. Since the late 20th century, a digital

core network A backbone or core network is a part of a computer network which interconnects networks, providing a path for the exchange of information between different LANs or subnetworks. A backbone can tie together diverse networks in the same buildin ...

has replaced the traditional

analog transmission Analog transmission is a transmission method of conveying information using a continuous signal which varies in amplitude, phase, or some other property in proportion to that information. It could be the transfer of an analog signal, using an an ...

and signaling systems, and much of the

has also been digitized. Starting with the development of

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

technology, originating from

Bell Telephone Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

in 1947, to amplification and

switching circuit Switching circuit theory is the mathematical study of the properties of networks of idealized switches. Such networks may be strictly combinational logic, in which their output state is only a function of the present state of their inputs; or may ...

s in the 1950s, the public switched telephone network (PSTN) has gradually moved towards

solid-state electronics Solid-state electronics means semiconductor electronics: electronic equipment using semiconductor devices such as transistors, diodes and integrated circuits (ICs). The term is also used as an adjective for devices in which semiconductor electr ...

and

automation Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...

. Following the development of

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

-based electronic switching systems incorporating

metal–oxide–semiconductor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

(MOS) and

pulse-code modulation Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM Stream (comp ...

(PCM) technologies, the PSTN gradually evolved towards the digitization of signaling and audio transmissions. Digital telephony has since dramatically improved the capacity, quality and cost of the network. Digitization allows

wideband 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 ...

on the same channel, with improved quality of a wider analog voice channel.

History

The earliest end-to-end analog telephone networks to be modified and upgraded to transmission networks with Digital Signal 1 (DS1/T1) carrier systems date back to the early 1960s. They were designed to support the basic 3 kHz voice channel by sampling the bandwidth-limited analog voice signal and encoding using

(PCM). Early PCM

codec A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or ...

filters Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

were implemented as passive resistor

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...

inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...

filter circuits, with

analog-to-digital In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...

conversion (for digitizing voices) and

digital-to-analog In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function. There are several DAC architec ...

conversion (for reconstructing voices) handled by discrete devices. Early digital telephony was impractical due to the low performance and high costs of early PCM codec-filters. Practical

digital telecommunication Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point or ...

was enabled by the invention of the

metal–oxide–semiconductor field-effect transistor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

(MOSFET), which led to the rapid development and wide adoption of PCM digital telephony. The MOSFET was invented by

Mohamed M. Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physicist, cryptographer, inventor and entrepreneur. He was a semiconductor pioneer who made important contributions to ...

and

Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics. He is best known for inventing the MOSFET (metal–oxide–semiconductor field-effe ...

in 1959, and the

(MOS)

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

(IC) chip was proposed soon after, but MOS technology was initially overlooked by Bell because they did not find it practical for analog telephone applications, before it was commercialized by

Fairchild Fairchild may refer to: Organizations * Fairchild Aerial Surveys, operated in cooperation with a subsidiary of Fairey Aviation Company * Fairchild Camera and Instrument * List of Sherman Fairchild companies, "Fairchild" companies * Fairchild Fa ...

and

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

for

such as computers. MOS technology eventually became practical for telephone applications with the MOS

mixed-signal integrated circuit A mixed-signal integrated circuit is any integrated circuit that has both analog circuits and digital circuits on a single semiconductor die.digital signal processing on a single chip, developed by former Bell engineer

David A. Hodges David Albert Hodges (1937–2022) was an American electrical engineer, digital telephony pioneer, and professor of electrical engineering at the University of California, Berkeley. Hodges was elected a member of the National Academy of Engineering ...

with Paul R. Gray at

UC Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant uni ...

in the early 1970s. In 1974, Hodges and Gray worked with R.E. Suarez to develop MOS switched capacitor (SC) circuit technology, which they used to develop a

digital-to-analog converter In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function. There are several DAC archit ...

(DAC) chip, using

MOS capacitor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

s and MOSFET switches for data conversion. MOS

analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...

(ADC) and DAC chips were commercialized by 1974. MOS SC circuits led to the development of PCM codec-filter chips in the late 1970s. The

silicon-gate In Semiconductor device fabrication, semiconductor electronics fabrication technology, a self-aligned gate is a transistor manufacturing approach whereby the gate (transistor), gate electrode of a MOSFET (metal–oxide–semiconductor field-effec ...

CMOS (complementary MOS) PCM codec-filter chip, developed by Hodges and W.C. Black in 1980, has since been the industry standard for digital telephony. By the 1990s,

telecommunication network A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, mess ...

s 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 telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...

, private branch exchanges (PBX) and

key telephone system A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone syst ...

s (KTS); user-end

modems A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more ca ...

;

data transmission Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point o ...

applications such as

digital loop carrier A digital loop carrier (DLC) is a system which uses digital transmission to extend the range of the local loop farther than would be possible using only twisted pair copper wires. A DLC digitizes and multiplexes the individual signals carried by t ...

pair gain In telephony, pair gain is the transmitting of multiple POTS signals over the twisted pairs traditionally used for a single traditional subscriber line in telephone systems. Pair gain has the effect of creating additional subscriber lines. This ...

multiplexers, telephone loop extenders,

integrated services digital network Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work ...

(ISDN) terminals, digital

cordless telephones A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short ...

and digital

cell phones A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...

; and applications such as

speech recognition Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers with the m ...

equipment, voice data storage,

voice mail A voicemail system (also known as voice message or voice bank) is a computer-based system that allows users and subscribers to exchange personal voice messages; to select and deliver voice information; and to process transactions relating to ind ...

and digital tapeless

answering machines An answering machine, answerphone or message machine, also known as telephone messaging machine (or TAM) in the UK and some Commonwealth countries, ansaphone or ansafone (from a trade name), or telephone answering device (TAD), was used for a ...

. The bandwidth of digital telecommunication networks has been rapidly increasing at an exponential rate, as observed by Edholm's law, largely driven by the rapid scaling and miniaturization of MOS technology. Uncompressed PCM

digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, sa ...

with 8-bit depth and 8

kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

sample rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or spa ...

requires a bit rate of 64

kbit/s In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are multi ...

, which was impractical for early digital telecommunication networks with limited

network bandwidth In computing, bandwidth is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth, data bandwidth, or digital bandwidth. This definition of ''bandwidth'' is in contrast to the field of signal p ...

. A solution to this issue was

linear predictive coding Linear predictive coding (LPC) is a method used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model. ...

(LPC), a

speech coding Speech coding is an application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic d ...

data compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressio ...

algorithm that was first proposed by

Fumitada Itakura is a Japanese scientist. He did pioneering work in statistical signal processing, and its application to speech analysis, synthesis and coding, including the development of the linear predictive coding (LPC) and line spectral pairs (LSP) method ...

of Nagoya University and Shuzo Saito of

Nippon Telegraph and Telephone , commonly known as NTT, is a Japanese telecommunications company headquartered in Tokyo, Japan. Ranked 55th in Fortune Global 500, ''Fortune'' Global 500, NTT is the fourth largest telecommunications company in the world in terms of revenue, as w ...

(NTT) in 1966. LPC was capable of

audio data compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressi ...

down to 2.4kbit/s, leading to the first successful real-time conversations over digital networks in the 1970s. LPC has since been the most widely used speech coding method. Another

method, a discrete cosine transform (DCT) algorithm called the modified discrete cosine transform (MDCT), has been widely adopted for speech coding in

voice-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 t ...

(VoIP) applications since the late 1990s. The development of transmission methods such as

SONET Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diode ...

and

fiber optic An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means t ...

transmission further advanced digital transmission. 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 In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...

on the transmission medium. Today the end instrument often remains analog but the analog signals are typically converted to

digital signals A digital signal is a Signal (electrical engineering), signal that represents data as a sequence of discrete space, discrete values; at any given time it can only take on, at most, one of a finite number of values. This contrasts with an analog ...

at the

serving area interface The serving area interface or service area interface (SAI) is an outdoor enclosure or metal box that allows access to telecommunications wiring. Alternate names *Access point (AP) *Cabinet (cab) *B-box (breakout box) *Cross box *Cross-connect b ...

(SAI), central office (CO), or other aggregation point.

Digital loop carrier A digital loop carrier (DLC) is a system which uses digital transmission to extend the range of the local loop farther than would be possible using only twisted pair copper wires. A DLC digitizes and multiplexes the individual signals carried by t ...

s (DLC) and fiber to the x place the digital network ever closer to the customer premises, relegating the analog

to legacy status.

IP telephony

The field of technology available for telephony has broadened with the advent of new communication technologies. Telephony now includes the technologies of Internet services and mobile communication, including video conferencing. The new technologies based on

Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. ...

(IP) concepts are often referred to separately as voice over IP (VoIP) telephony, also commonly referred to as IP telephony or Internet telephony. Unlike traditional phone service, IP telephony service is relatively unregulated by government. In the United States, the Federal Communications Commission (FCC) regulates phone-to-phone connections, but says they do not plan to regulate connections between a phone user and an IP telephony service provider. A specialization of digital telephony, Internet Protocol (IP) telephony involves the application of digital networking technology that was the foundation to the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

to create, transmit, and receive telecommunications sessions over

computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

s. Internet telephony is commonly known as

(VoIP), reflecting the principle, but it has been referred with many other terms. VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone infrastructure technologies. As of January 2005, up to 10% of telephone subscribers in

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

and

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

have switched to this digital telephone service. A January 2005 ''

Newsweek ''Newsweek'' is an American weekly online news magazine co-owned 50 percent each by Dev Pragad, its president and CEO, and Johnathan Davis, who has no operational role at ''Newsweek''. Founded as a weekly print magazine in 1933, it was widely ...

'' article suggested that Internet telephony may be "the next big thing". As of 2006, many VoIP companies offer service to

consumer A consumer is a person or a group who intends to order, or uses purchased goods, products, or services primarily for personal, social, family, household and similar needs, who is not directly related to entrepreneurial or business activities. ...

s and

business Business is the practice of making one's living or making money by producing or Trade, buying and selling Product (business), products (such as goods and Service (economics), services). It is also "any activity or enterprise entered into for pr ...

es. IP telephony uses an Internet connection and hardware

IP phone 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. This is in contrast to a standard phone which uses the traditional public switched telephone network ...

s, analog telephone adapters, or

softphone A softphone is a software program for making telephone calls over the Internet using a general purpose computer rather than dedicated hardware. The softphone can be installed on a piece of equipment such as a desktop, mobile device, or other comp ...

computer applications to transmit conversations encoded as

data packet In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the '' payload''. Control inform ...

s. In addition to replacing plain old telephone service (POTS), IP telephony services compete with

mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...

services by offering free or lower cost connections via

WiFi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wa ...

hotspots Hotspot, Hot Spot or Hot spot may refer to: Places * Hot Spot, Kentucky, a community in the United States Arts, entertainment, and media Fictional entities * Hot Spot (comics), a name for the DC Comics character Isaiah Crockett * Hot Spot (Tr ...

. VoIP is also used on private networks which may or may not have a connection to the global telephone network. Fixed telephone lines per 100 inhabitants 1997-2007 ITU

Fixed telephone lines per 100 inhabitants 1997-2007 ITU

Social impact research

Direct person-to-person communication includes non-verbal cues expressed in facial and other bodily articulation, that cannot be transmitted in traditional voice telephony.

Video telephony Videotelephony, also known as videoconferencing and video teleconferencing, is the two-way or multipoint reception and transmission of audio signal, audio and video signals by people in different locations for Real-time, real time communication. ...

restores such interactions to varying degrees. Social Context Cues Theory is a model to measure the success of different types of communication in maintaining the non-verbal cues present in face-to-face interactions. The research examines many different cues, such as the physical context, different facial expressions, body movements, tone of voice, touch and smell. Various communication cues are lost with the usage of the telephone. The communicating parties are not able to identify the body movements, and lack touch and smell. Although this diminished ability to identify social cues is well known, Wiesenfeld, Raghuram, and Garud point out that there is a value and efficiency to the type of communication for different tasks. They examine work places in which different types of communication, such as the telephone, are more useful than face-to-face interaction. The expansion of communication to mobile telephone service has created a different filter of the social cues than the land-line telephone. The use of instant messaging, such as ''texting'', on mobile telephones has created a sense of community. In ''The Social Construction of Mobile Telephony'' it is suggested that each phone call and text message is more than an attempt to converse. Instead, it is a gesture which maintains the social network between family and friends. Although there is a loss of certain social cues through telephones, mobile phones bring new forms of expression of different cues that are understood by different audiences. New language additives attempt to compensate for the inherent lack of non-physical interaction. Another social theory supported through telephony is the Media Dependency Theory. This theory concludes that people use media or a resource to attain certain goals. This theory states that there is a link between the media, audience, and the large social system. Telephones, depending on the person, help attain certain goals like accessing information, keeping in contact with others, sending quick communication, entertainment, etc.

References

{{Authority control History of telecommunications Telecommunications