TDM was invented so voice traffic that is carried over a medium can be maximized. For multiple signals to share a medium, the medium must be somehow divided. In TDM the users take turns, where each has a turn to have an exclusive use of the medium in a round robin fashion. TDM works under the physical layer, and it divides the bandwidth of a single link by separating channels or time slots. TDM transmits two or more channels over the same link by allocating a different time interval (time slot) for the transmission of each channel. The channels are each given a regular time slot in which they send a PCM signal. TDM increases the capacity of the transmission link by slicing time into smaller intervals so that the link carries the bits from multiple input sources, effectively increasing the number of bits transmitted per second. With TDM, the transmitter and the receiver both know exactly which signal is being sent.
TDM is used for digital signals or analog signals to carry digital data. The Data Rate of the transmission media has to exceeds the data rate of the signals for the TDM system to work. It also uses a frame where numbers of bits and bytes are put together to form one particular unit at in order to send data over.
An example of a technology that uses synchronous TDM is ISDN & SONET
Just like many technology out there TDM has its disadvantage. The disadvantage is that is a lot of bandwidth is wasted the TDM system is used.
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