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Digital switch

Digital switch

Digital switch definition

A digital switch is a piece of hardware that manages the digital signals of a telephone exchange and forwards them to a back-end network. Digital switches help establish communications between customers of telephony services.

Digital switches are considerably faster than analog switches, but they can only handle binary signals (that is, the state of the signal must be “0” or “1”).

Main digital switch types

  • Time switch: In a time switching setup, the incoming 8-bit pulse-code modulations (PCM) can be forwarded to any output time slot. The input PCM word is recorded in the switch memory and read out as per the request.
  • Space switch: In a space switching setup, the 8-bit PCM holds its time slot during and after switching, preventing delay.

Examples of digital switching systems

  • AXE telephone exchange (Ericsson): The most popular digital switching system in the world, developed in Sweden in 1974.
  • E10 (Alcatel): Developed in France in the late 1960s, E10 is one of the earliest time division multiplexing (TDM) switches to be adopted for public networks, prompting the shift from analog switching to digital switching.
  • EWSD (Nokia Siemens Networks): A digital switching system developed for the German market in 1975.
  • System X (Marconi): A digital switching system developed in 1980 for the UK market and used primarily by the BT Group.

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