ASYNCHRONOUS TRANSMISSION

ASYNCHRONOUS TRANSMISSION
Also called as star/stop transmission. A special start signal is transmitted at the beginning of each group of message bits- a group is usually just a single character. When the receiving device gets the start signal, it sets up a timing mechanism to accept the group of message bits.
SYNCHRONOUS TRANSMISSION
In this kind, characters are transmitted together in a continuous stream. There are no call-to-action signals for each character. Instead, the sending and the receiving devices are synchronized by having their internal clocks put in time with each other by a bit pattern transmitted at the beginning of the message. Furthermore, error check bits are transmitted at the end of each message to make sure all characters were received properly
NOTE:
* Synchronous transmission equipment is more complex and more expensive but, without all the start stop bits, transmission is much faster.