Intelecommunications, anelectronic switching system (ESS) is atelephone switch that usessolid-state electronics, such asdigital electronics andcomputerizedcommon control, 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 purelyelectro-mechanical relay systems and analog voice paths. These early machines typically utilized thestep-by-step technique. The first generation of electronic switching systems in the 1960s were not entirely digital in nature, but usedreed relay-operated metallic paths orcrossbar switches operated bystored program control (SPC) systems.
First announced in 1955, the first customer trial installation of an all-electroniccentral office commenced inMorris, Illinois in November 1960 byBell Laboratories.[1] The first large-scale electronic switching system was theNumber One Electronic Switching System (1ESS) of theBell System, cut over inSuccasunna,New Jersey, in May 1965.
Just three years later, in September 1968, Britain's Post Office opened the world's first all-digitalpulse-code modulation (PCM) exchange namedEmpress (three decades after British scientistAlec Reeves had invented the PCM encoding system without the digital components to take full advantage).[2] Other nations vying to reach the forefront of technical innovation would adoptmetal–oxide–semiconductor (MOS) and PCM technologies to make their own transitions from analog todigital telephony throughout the 1970s.[3][4] Later electronic switching systems implemented the digital representation of the electrical audio signals onsubscriber loops 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 thetelephone network.
With the advances of digital electronics starting in the 1960s telephone switches employedsemiconductor device components in increasing measure.
In the late 20th century most telephone exchanges without TDM processing were eliminated and the termelectronic switching system became largely a historical distinction for the older SPC systems.
This article incorporatespublic domain material fromFederal Standard 1037C.General Services Administration. Archived fromthe original on 2022-01-22. (in support ofMIL-STD-188).NANP telephone switches | |
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| Early automatic &crossbar switches | |
| Electronic switching systems | |
