telecommunications Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

, an electronic switching system (ESS) is a

telephone switch 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 ...

that uses

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

, such as

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. It deals with the relationship between Binary number, binary inputs and outputs by passing electrical s ...

and

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

ized

common control In telecommunications, common control is a principle of switching telephone calls in an automatic telephone exchange that employs shared control equipment which is attached to the circuit of a call only for the duration of establishing or otherwis ...

, to interconnect telephone circuits for the purpose of establishing telephone calls. The generations of telephone switches before the advent of electronic switching in the 1950s used purely

electro-mechanical Electromechanics combine processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focus on the interaction of electrical and mechanical systems as a whole and how the two systems interact with each ...

relay systems and analog voice paths. These early machines typically utilized the step-by-step technique. The first generation of electronic switching systems in the 1960s were not entirely digital in nature, but used

reed relay A reed relay is a type of relay that uses an electromagnet to control one or more reed switches. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Sealed in a long, narro ...

-operated metallic paths or

crossbar switch In electronics and telecommunications, a crossbar switch (cross-point switch, matrix switch) is a collection of switches arranged in a Matrix (mathematics), matrix configuration. A crossbar switch has multiple input and output lines that form a ...

es operated by

stored program control Stored program control (SPC) is a telecommunications technology for telephone exchanges. Its characteristic is that the switching system is controlled by a computer program stored in a memory in the switching system. SPC was the enabling technology ...

(SPC) systems. First announced in 1955, the first customer trial installation of an all-electronic central office commenced in

Morris, Illinois Morris is a city in and the county seat of Grundy County, Illinois, Grundy County, Illinois, United States and part of the southwest Chicago metropolitan area. The population was 14,163 as of the 2020 United States census, 2020 census. A team of ...

in November 1960 by

Bell Laboratories Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several lab ...

. The first large-scale electronic switching system was the Number One Electronic Switching System (1ESS) of the

Bell System The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the AT&T Corporation, American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America fo ...

, cut over in

Succasunna Succasunna is an Local government in New Jersey#Unincorporated communities, unincorporated community and census-designated place (CDP) in Roxbury, New Jersey, Roxbury Township, Morris County, New Jersey, United States, serving as the township's ...

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

, in May 1965. Just three years later, in September 1968, Britain's Post Office opened the world's first all-digital

pulse-code modulation Pulse-code modulation (PCM) is a method used to digitally represent 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, the amplitud ...

(PCM) exchange named ''Empress'' (three decades after British scientist

Alec Reeves Alec Harley Reeves (10 March 1902 – 13 October 1971) was an English scientist best known for his invention of pulse-code modulation (PCM). He was awarded 82 patents. Early life Alec Reeves was born in Redhill, Surrey in 1902 and was educated ...

had invented the PCM encoding system without the digital components to take full advantage). Other nations vying to reach the forefront of technical innovation would adopt

metal–oxide–semiconductor upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale. In electronics, the metal–oxide–semiconductor field- ...

(MOS) and PCM technologies to make their own transitions from analog to

digital 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 ...

throughout the 1970s. Later electronic switching systems implemented the digital representation of the electrical audio signals on

subscriber 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 comm ...

s by digitizing the analog signals and processing the resulting data for transmission between central offices. Time-division multiplexing (TDM) technology permitted the simultaneous transmission of multiple telephone calls on a single wire connection between central offices or other electronic switches, resulting in dramatic capacity improvements of the

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 internet. The idea was revolutionized in the 1920s, as more and more ...

. With the advances of digital electronics starting in the 1960s telephone switches employed

semiconductor device A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its conductivit ...

components in increasing measure. In the late 20th century most telephone exchanges without TDM processing were eliminated and the term ''electronic switching system'' became largely a historical distinction for the older SPC systems.

References

* {{Telephone Switches Telephone exchanges

See also

References