Saturday, May 22, 2010

Multiplexer,concentrators,and controllers

Like message switchers, a multiplexer allows severals terminals to use one line to communucate with a CPU. However, it allow the terminals to send their messages simultaneously. A multiplexer, in other words, collects message from various senders, put them in order, and transmits them along a broadband channel at very high speeds to the receiver.
A concentrators is essentially a smart multiplexer- it can be programmed, has more processing capability, and is more flexible than a multiplexer.
Controller or cluster controllers, link groups of terminals or other devices to a communications channels. The controller polls the status of each terminals and transfers data from a terminal to the host computer when necessary.
Multiplexers, concentrators and controllers are frequently used at termainals sites having heavy input and output requriements.

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