What is time multiplexed space switching? With a neat diagram explain its operation.

What is time multiplexed space switching? With a neat diagram explain its operation.
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Time division switches where an inlet or an outlet 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 that are required in transit exchanges. Here, the inlets and outlets are trunks which carry time division multiplexed data streams. We call such switches time multiplexed switches. A time multiplexed time division space switch is shown in Fig. There are N incoming trunks and N outgoing trunks, each carrying a time division multiplexed stream of M samples per frame. Each 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 usually referred to as a time slot. In one time slot, N samples are switched. Fig shows an output-controlled switch. The output is cyclically scanned. There is a 1-to-M relationship between the outlets and the control memory locations, i.e. there are M locations in the control memory corresponding to each outlet.

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The control memory has MN words. If we view the control memory as M blocks of N words each, a location address may 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 < M and 1< j < N. The block address i corresponds to the time slot i and the word address j to the outlet j. The first N locations of the control memory correspond to the first time slot, the next N locations, i.e. locations N + 1 to 2N when addressed linearly, or locations (2,1) to (2,N) when addressed in a two dimensional form, correspond to the time slot 2 and so on. Therefore, if the location (i,j) contains an inlet address k, it implies that inlet k is connected to the outlet j during the time slot i. The number of trunks that can be supported on this switch is given by N =125/ Mt , Where t is the switching time including memory access time per inlet-outlet pair.  

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Related questions

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