In the Synchronous Time Division Multiplexing (STDM), the multiplexer assigns an equal time slot to every device at all times, whether or not a device has anything to send. Time slot A, for instance, is authorised to device A alone and cannot be used by any other device.
Each time is assigned a time slot and it shows up. Then, a device has the time to transmit a portion of its data. If a device cannot send or does not have data to send, its time slot remains null.
The time slots are consolidated into frames, and every frame includes one or more time slots committed to each sending device. If there are n sending devices, the frame consists of n slots, where each slot will be allocated to each of the sending devices. This happens if all the sending devices transmit at the same rate as shown in the figure.
In the diagram given below, there are four inputs to multiplexer A. Each frame is having four slots corresponding to each of the sending devices.
Synchronous Time Division Multiplexing (TDM) can be distinguished to a high-speed rotating switch. As the switch is free in front of a device, that device can transmit a particular record of data onto the direction. The switch transfers from device to device at a fixed price and in a permanent order. This process is called interleaving.
At the receiver, the demultiplexer disintegrates every frame by obtaining each character in turn. As a character is eliminated from a frame, it is moved to the suitable receiving device, as demonstrated in the figure below.
The disadvantages of Synchronous TDM are as follows −
In synchronous time-division multiplexing, an equal time slot is given to each sender to load its data on the channel.
Different senders load different volumes of data, and frames are usually empty.