Asynchronous transmission uses start and stop bits to signify the beginning and end of a transmission. This means that an 8 bit ASCII character with a parity bit would actually be transmitted using 10 bits. This method of transmission is used when data is sent intermittently as appose to in a solid stream. In the following example the start and stop bits are in bold. The start and stop bits must be of opposite polarity. This allows the receiver to recognise when the second packet of information is being sent.
Thus may say a method of sending data in irregular time intervals using a code such as ASCII. ATM allows most modern computers to communicate with one another easily.