Error Detecting Code - Parity bit:

The general idea for achieving error detection and correction is to add some redundancy (i.e., some extra data) to a message, which receivers can use to check consistency of the delivered message, and to recover data determined to be erroneous. An error-detection scheme may be combined with a system for retransmissions of erroneous data

 A parity bit is a bit that is added to a group of source bits to ensure that the number of set bits (i.e., bits with value 1) in the outcome is even or odd. It is a very simple scheme that can be used to detect single error in the output.

Fig. Transmit data using a parity bit