Synchronous transmission

Synchronous transmission is when we send data in time with a clock signal.

One signal is sent each time the clock pulses, so the sender and receiver are synchronised to the same clock signal.

That way, they can both know when to send and receive data, without needing to send extra signals to indicate when data is being sent.

This does mean that the sender and receiver need to be synchronised to the same clock signal, and they need to always be listening to the clock signal, even when no data is being sent.

The advantage though is that, once they’re synchronised, they can just send data. They don’t need to send any extra signals like start and stop bits, or wait for the receiver to be ready, etc. They can just send data whenever they want, and the receiver will know when to receive it.
That makes synchronous transmission faster than asynchronous transmission, because there’s no overhead of sending extra signals.