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Difference between TDM and FDM

Following are the difference between  time division multiplexing and frequency division multiplexing.

TDM FDM
TDM stands for time division multiplexing. FDM stands for frequency division multiplexing.
TDM is preferred for the digital signals. FDM is preferred for digital signals.
The signals to be multiplexed can occupy the entire bandwidth but they are isolated in the time domain. The signals to be multiplexed are added in time domain. But they occupy different slots in the frequency domain.
Synchronization is required. Synchronization is not required.
Cross talk like problem not occurs in TDM. It suffers from cross-talk like problems due to imperfect band pass filter.
Only a few TDM channels will be affected due to fading. Due to wideband fading in the transmission medium, all the FDM channels are affected.