Asynchronous Transmission
Asynchronous transmission is often referred to as start-stop transmission because the transmitting device can transmit a character whenever it is convenient, and the receiving device will accept that character
each character is transmitted independently
In order to separate the characters and synchronize transmission, a start bit and a stop bit are put on each end of each individual character (e.g., 1 start bit, 7 bits for the letter, 1 parity bit, 1 stop bit)
typically used in point-to-point full duplex circuits)