Time Division Multiplexing (TDM)
The process called multiplexing is used in order to utilize common transmission channel or medium to transmit more than one sig
TDM is a digital multiplexing process.
In TDM, all sig to be transmitted are not transmitted simultaneously. Instead they are transmitted one by one.
Thus each sig will be transmitted for a very short time. One cycle or frame is said to be complete when sigs are transmission channel. The TDM principle is :
Transmission of each channel completes one cycle of operations called as “frame”
The TDM system can be used to multiplexer analog or digital signals, however it is more suitable for the digital multiplexing.
The concept of TDM will be more clear if refer fig.
The one unit from each source is taken and combined to form one frame. The size of each unit such as $A_1,B_1$ etc can be 1 bit or several bits
For 3 i/p being multiplexed, a frame of TDM will consists of 3 units, i.e., one unit from each source.
Similarly for n numbers of i/p, each TDM frame will consist of n units.
It is transmitted on common communication medium:
It is always in times the data rates of individual sources, where n is no. of sources
So if there sources are being multiplexed, then data rate of TDM sig is three times higher than individual data rate.
Naturally the duration of every unit $(A_1$ or $B_1)$ in TDM sig i.e n times shorter than the unit duration before multiplexing