Sketch for an algebra of relay and contactor circuits

A system of symbols is described, by which the various elements (contacts and operating coils) of a relay circuit can be represented. The symbols are then linked together by signs, the resultant algebraic expression corresponding to the circuit, and the operation of the circuit can be studied by considering the behaviour of the algebraic expression according to rules which are developed in the paper. Methods are described whereby complex circuits may be simplified by algebraic manipulation of the symbolic expressions; and design of relay circuits to perform given operations is discussed.