Draw diag of TDM - PCM system and explain.

Similar Question - With block diag explain TDM – PCM system.

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PCM – TDM system

When a large no. of PCM signals are to be transmitted over a common channel, multiplexing of these PCM signals is required. Fig shows basic time division multiplexing scheme for PCM voice channels called as $T_1$ digital system. This system is used to convey a number of voice signals over telephone line using wideband coaxial cable.

Operation of $T_1$ system :

The operation of PCM – TDM system is :

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This system has been designed to multiplex 24 voice channels marked as $S_1$ to $S_{24}$. Each signal is bandlimited to S.3 kHz and sampling is done at a standard rate of 8kHz. This sampling rate is higher than the Nyquist rate. The sampling is done by coomutator switch $Sw_1$

These voice signals are selected one by one and connected to a PCM transmitter by the commutator switch $Sw_1$ as it complets its rotation. The commutator switch remains in contact with each voice channel for a short time. Thus it samples each of 24 channels.

Periodically, after every 6000 ft. the PCM –TDM signal is regenerated by amplifiers called “repeaters”.

They eliminate the distortion introduced by channel and remove the superimposed noise and regenerate a clean noise free PCM –TDM signal at their o/p. This ensures that received sig is free from the distortions and noise.

The destination the signal is compounded, decoded and de multiplexed, using PCM receiver.

Synchronization between the transmitter and receiver commutators $Sw_1$ and $Sw_2$ is essential in order to ensure proper communications.

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