|Shannon, Claude (1938). A Symbolic Analysis of Relay and Switching Circuits. Transactions American Institute of Electrical Engineers. vol. 57, 1938. S. 476.|
Any expression formed with the operations of addition, multiplication, and negation represents explicitly a circuit containing only series and parallel connections. Such a circuit will be called a series-parallel circuit. Each letter in an expression of this sort represents a make or break relay contact, or a switch blade and contact. To find the circuit requiring the least number of contacts, it is therefore necessary to manipulate the expression into the form in which the least number of letters appear. The theorems given above are always sufficient to do this. A little practice in the manipulation of these symbols is all that is required.