Define the Half Duplex Transmission

A half-duplex channel can receive andsend, but not at the same time. It's like a one-lane bridge where two-way traffic should give way in order to cross. Only one end transmits at a time, other end receives. Asynchronous means 'no synchronization' and thus doesn't require receiving and sending idle characters. Though the beginning and end of each byte of data should be identified by start and stop bits. Start bit indicates when data byte is about to begin and stop bit signals when it ends. Requirement to send these extra two bits causes asynchronous communication to be slightly slower than synchronous but it has the advantage that processor doesn't have to deal with the extra idle characters.