data communication Data communication, including data transmission and data reception, is the transfer of data, transmitted and received over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optic ...

s, an automatic switching system is a switching system in which all the operations required to execute the three phases of information-transfer 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 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 International Advisors, a h ...

and the disengagement phase by a user. In

telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...

, it refers to a

telephone exchange A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits ...

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

telephone call A telephone call, phone call, voice call, or simply a call, is the effective use of a connection over a telephone network between the calling party and the called party. Telephone calls are the form of human communication that was first enabl ...

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