data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted ...

communications Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...

, an automatic switching system is a switching system in which all the operations required to execute the three phases of

Information transfer In telecommunications, information transfer is the process of moving messages containing user information from a source to a sink via a communication channel. In this sense, information transfer is equivalent to data transmission which highlights ...

transactions are automatically executed in response to signals from a

user Ancient Egyptian roles * User (ancient Egyptian official), an ancient Egyptian nomarch (governor) of the Eighth Dynasty * Useramen, an ancient Egyptian vizier also called "User" Other uses * User (computing), a person (or software) using an ...

end-instrument. In an automatic switching system, the

information-transfer transaction A transaction is a change of state, an information-transfer transaction is a transaction in which one of the following changes occurs: content, ownership, location, format, etc. An information-transfer transaction usually consists of three consecut ...

is performed without human intervention, except for initiation of the

access phase Access may refer to: Companies and organizations * ACCESS (Australia), an Australian youth network * Access (credit card), a former credit card in the United Kingdom * Access Co., a Japanese software company * Access Healthcare, an Indian BPO se ...

and the

disengagement phase The term disengagement can refer to: * Apathy * Disengagement theory in gerontology * Moral disengagement * Religious disengagement * Social disengagement * Disengagement (military) * Disengagement (engineering) * Disengagement (politics) ** Isr ...

by a user. In

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 ...

, it refers to a

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 ...

in which all the operations required to set up, supervise, and release connections required for

telephone call A telephone call is a connection over a telephone network A telephone network is a telecommunications network that connects telephones, which allows telephone calls between two or more parties, as well as newer features such as fax and interne ...

s are automatically performed in response to signals from a calling device. This distinction lost importance as manual switching declined during the 20th century.

References

{{Reflist Telephone exchange equipment