Switching in Telecommunications
Evolution of Telecommunications
Switching Equipment
The evolution of telecommunications switching equipment progressed through the following three distinct phases.
Strowger Switches
These were the earliest switches and were constructed using relays. Connections within these switches were made as a step by step process, i.e., after each digit was received.
Crossbar Switches
These switches used miniaturised relays and could support a number of simultaneous connections. Connections in these switches were established after the entire destination number had been received.
Digital Processor Controlled Switches
These switches employ computers that control the interconnections. These switches have significant intelligence to perform complex operations, such as selection of best routes for different types of connections. These may be programmed to provide multiple facilities to users. For example, call transfer, line transfer, teleconferencing etc. These switches have high reliability and significantly reduced sizes.
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© Omar Bashir, December 1998