Download - Digital Switching Principles
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Digital Switching Principles
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Digital Switching
• The digital signals of several speech / datasamples are time multiplexed on a common media before being switched through the system.
• To connect any two subscribers, it is necessary to interconnect the time-slots of the two speech samples which may be on same or different PCM highways.
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• The digitalised speech samples are switched in two modes, viz.,
• Time Switching and • Space Switching.
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Space Switching
• In the space-switching mode, corresponding time-slots of I/C and O/G PCM highways are interconnected.
• A sample, in a given time-slot, TSi of an I/C HWY, say HWY1, is switched to same time-slot, TSi of an O/G HWY, SAY HWY2.
• Obviously there is no delay in switching of the sample from one highway to another highway since the sample transfer takes place in the same time-slot of the PCM frame.
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Digital Time Switch
• A Digital Time Switch consists of two memories, viz., a speech or buffer memory to store the samples till destination time-slots arrive, and
• a control or connection or address memory to control the writing and reading of the samples in the buffer memory and directing them on to the appropriate time-slots.
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• Time switch can operate in two modes, viz.,• I. Output associated control • ii. Input associated control
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OUTPUT ASSOCIATED CONTROL SWITCH
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INPUT ASSOCIATED CONTROL SWITCH
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T S T SWITCH
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T S T SWITCH STRUCTURE
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