Differential Manchester encoding

Differential Manchester encoding is a method of encoding data in which (a) data and clock signals are combined to form a single self-synchronizing data stream, (b) one of the two bits, i.e., "0" or "1", is represented by no transition at the beginning of a pulse period and a transition in either direction at the midpoint of a pulse period, and (c) the other is represented by a transition at the beginning of a pulse period and a transition at the midpoint of the pulse period.

A related method is Manchester encoding in which transitions always occur in the same directions for the bit encodings 0 and 1.

Note: In differential Manchester encoding, if a "1" is represented by one transition, a "0" is represented by two transitions, and vice versa.

Source: from Federal Standard 1037C