Telephony

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Telephony

In telecommunication

Telecommunication

Telecommunication is the assisted Transmission of Signal over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, Drum , Semaphore line, flag signals or heliograph....
, telephony ( or teh-LEH-fuh-nee) encompasses the general use of equipment to provide voice communication over distances, specifically by connecting telephone

Telephone

The telephone is a telecommunications device that is used to transmitter and receive electronically or digitally encoded sound between two or more people conversing....
s to each other.

Telephones were originally connected directly together in pairs. Each user had separate telephones wired to the various places he might wish to reach. This became inconvenient when people wanted to talk to many other telephones, so the telephone exchange

Telephone exchange

In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls....
was invented.

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Encyclopedia

In telecommunication

Telecommunication

Telephone

Telephone exchange

In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls....
was invented. Each telephone could then be connected to other local ones, thus inventing the local loop

Local loop

In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the Customer-premises equipment to the edge of the Common carrier or telecommunications service provider's network....
and the telephone call

Telephone call

A telephone call is a connection over a telephone network between the calling party and the called party....
. Soon, nearby exchanges were connected by trunk lines

Trunking

Trunking is a concept in modern communications by which a communications system can provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually....
, and eventually distant ones were as well.

In modern times, most telephones are plugged into telephone jacks. Each jack is connected by inside wiring

On-premises wiring

In telecommunication, on-premises wiring is customer-owned metallic or optical fiber telecommunication transmission lines, installed within or between buildings....
to a drop

Drop (telecommunication)

Drop, in telecommunication, has several meanings.In a communications network, a drop is the portion of a device directly connected to the internal station facilities, such as toward a telephone switchboard, toward a switching center, or toward a telephone exchange....
wire and then to a cable with other wires. Cables usually bring a large number of wires from all over a district access network

Access network

An access network is that part of a Telecommunication telecommunications network which connects subscribers to their immediate service provider....
to one wire center or telephone exchange. When the user of a telephone wants to make a telephone call

Telephone call

A telephone call is a connection over a telephone network between the calling party and the called party....
, equipment at the exchange examines the dialed telephone number

Telephone number

A telephone number or phone number is a sequence of numbers used to call from one telephone line to another in a telephone network. When telephone numbers were invented, they were short - as few as two or three digits - and were used by people to call a few neighbors....
and connects that telephone line

Telephone line

A telephone line or telephone circuit is a single-user telecommunication circuit on a telephone telecommunication system. Typically this refers to the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purpo...
to another in the same wire center, or to a trunk to a distant exchange. Most of the exchanges in the world are connected to each other, forming the Public Switched Telephone Network

Public switched telephone network

The public switched telephone network is the network of the world's public circuit switching telephone networks, in much the same way that the Internet is the network of the world's public Internet protocol-based packet switching networks....
or PSTN. By the end of the 20th century almost all were Stored Program Control exchange

Stored Program Control exchange

Stored Program Control exchange is the technical name used for telephone exchanges controlled by a computer program stored in the memory of the system....
s.

After the middle 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.

Digital telephony

Digital telephony

Digital telephony is the use of digital electronics in the provision of digital telephone services and systems. Since the 1960s a digital core network has almost entirely replaced the old Analog signal system, and much of the access network has also been digitized....
is the use of digital technology in the provision of telephone services and systems. Almost all telephone calls are provided this way, but sometimes the term is restricted to cases in which the last mile

Last mile

The "last mile" is the final leg of delivering connectivity from a communications provider to a customer. Usually referred to by the telecommunications and cable television industries....
is digital, or where the conversion between digital and analog signals takes place inside the telephone. Telephony was digitized to cut the cost and improve the quality of voice services, but digital telephony was then found useful for new network services (ISDN) to transfer data speedily over telephone lines.

IP Telephony is a modern form of telephony which uses the TCP/IP protocol popularized by the internet

Internet

The Internet is a global network of interconnected computers, enabling users to share information along multiple channels. Typically, a computer that connects to the Internet can access information from a vast array of available server and other computers by moving information from them to the computer's local memory....
to transmit digitized voice data. Contrast this with the operation of POTS (an acronym for "Plain Old Telephone Service

Plain old telephone service

Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in most parts of the world....
").

Computer Telephony Integration (CTI)

Computer telephony integration

Computer telephony integration, also called computer-telephone integration or CTI, is technology that allows interactions on a telephone and a computer to be integrated or co-ordinated....
enables computers to know about and control phone functions such as making and receiving voice, fax, and data calls with telephone directory services and caller identification. The integration of telephone software and computer systems is a major development in the evolution of the automated office.

CTI is not a new concept. Such links have been used in the past in large telephone networks but only dedicated call centers could justify the costs of the required equipment installation. Primary telephone service providers are offering information services such as Automatic Number Identification

Automatic number identification

Automatic Number Identification is a feature of telephony intelligent network Custom Local Area Signaling Services that permits subscribers to display or capture the telephone numbers of calling parties....
and Dialed Number Identification Service

Dialed Number Identification Service

Dialed Number Identification Service is a service sold by telecommunications companies to corporate clients that lets them determine which telephone number was dialed by a customer....
on a scale wide enough for its implementation to bring real value to business or residential telephone usage. A new generation of applications (middleware) is being developed as a result of standardization and availability of low cost computer telephony links.

Telephony

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