5ESS switch

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The 5ESS Switch is a Class 5 telephone electronic switching system sold by Alcatel-Lucent. This digital central office telephone circuit switching system is used by many telecommunications service providers.



The 5ESS Class 5 Switch first appeared in Seneca, Illinois (815 Area Code) in 1982, and slowly replaced the 1ESS switch and other electromechanical and analog systems in the 1980s and 1990s. The 5ESS was also used as a Class 4 telephone switch or as a mixed Class 4/5 in markets too small for a 4ESS switch. Approximately half of all U.S. telephone exchanges are serviced by 5ESS switches. The 5ESS is also exported internationally, and manufactured outside of the U.S. under license.

Lucent Technologies (now part of Alcatel-Lucent) was formerly the AT&T Network Systems division of AT&T, which in turn was formerly known as Western Electric. The 5ESS came to market as the Western Electric 5ESS, and was most recently marketed under the Alcatel-Lucent name.


5ESS has three main kinds of Module: AM is Administrative Module, which contains the central computers. CM is Communications Module, which is the central time-divided switch of the system. SM is Switching Module which in most exchanges is the majority of equipment. SM performs multiplexing, analog/digital coding, and other work to interface with the outside world. Each has a controller, a small computer whose CPUs and memories, like most common equipment of the exchange, are duplicated for redundancy. Distributed system lessens the load on the Central Administrative Module (AM) or main computer.

Power for all circuitry is distributed as −48VDC (nominal) and converted to logic or telephone voltages as needed by DC to DC converters on each shelf of circuit packs.

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