In data transmission, Manchester encoding is a form of digital encoding in which data bits are represented by transitions from one logical state to the other. This is different from the more common method of encoding, in which a bit is represented by either a high state such as +5 volts or a low state such as 0 volts.
When the Manchester code is used, the length of each data bit is set by default. This makes the signal self-clocking. The state of a bit is determined according to the direction of the transition. In some systems, the transition from low to high represents logic 1, and the transition from high to low represents logic 0. In other systems, the transition from low to high represents logic 0, and the transition from high to low represents logic 1.
The chief advantage of Manchester encoding is the fact that the signal synchronizes itself. This minimizes the error rate and optimizes reliability. The main disadvantage is the fact that a Manchester-encoded signal requires that more bits be transmitted than those in the original signal.