Data communication using combinations of lines

摘要

A signalling system utilising three or more conductors to convey symbols between an encoder and a decoder is disclosed. For each symbol a forward current or signal is transmitted down one of the wires and a reverse current is transmitted down one of the others. The other wires are held having no signal transmitted on them. The symbols are distinguished by which two conductors have signals on them and by the sense of those signals. The system may be used to transmit data in the form of binary bits by taking a set of n binary bits and converting them to one of 2 &circ& n of the available symbols. The number of symbols available is generally not an exact power of two and spare symbols are used to convey other information along the wires, for example, that no valid data is being transmitted at the present time. <IMAGE>