Synchronous transmission eliminates the need for start & stop bits up synchronizing the clocks on the transmitting & receiving devices. This synchronization is accomplished in two ways:
By transmitting synchronization signals with data. Some data encoding techniques, by guaranteeing a signal transition with each bit transmitted, are inherently self-clocking.
By using a separate communication channel to carry clock signals. This technique can function with any signal-encoding technique.
Illustrates the two possible structures of message associated with synchronous transmission.