Explain time multiplexed space switching? With a neat diagram illustrate its operation.

Ans:

Time division switches where an outlet or an inlet corresponded to a single subscriber line with one speech sample appearing every 125 µs on the line. Such switches are used in local exchanges. We now consider switches which are essential in transit exchanges. Here inlets and outlets are trunks that carry time division multiplexed data streams. We call these switches time multiplexed switches. A time multiplexed time division space switch is displayed in Figure. There are N incoming trunks and N outgoing trunks, each one carrying a time division multiplexed stream of M samples per frame. Every frame is of 125-µs time duration. In one frame time, a total of MN speech samples have to be switched. One sample duration, 125/M microseconds, is generally referred to as a time slot. In one time slot, N samples are switched. Figureillustrates an output-controlled switch. Output is cyclically scanned. There is a 1-to-M relationship between outlets and control memory locations, it implies that there are M locations in the control memory corresponding to each outlet.

Control memory has MN words. If we view control memory as M blocks of N words each, a location address can be specified in a two dimensional form (i,j)where i is the block address and j is the word within the block. We have 1< i

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