Session 1(b): Basic Techniques—Electronics: A Review of Postal Engineering Logic Units

Abstract

The paper describes why control elements using discrete components mounted on a printed circuit board were chosen for postal mechanization equipments. Basic design considerations are listed, and principles determining the choice of components stated. The decision to provide both ‘nor’ and ‘not-and’ elements is explained, and the reasons given why negative logic is used. With the use of B.S. symbols it is shown how logic diagrams can easily be converted to functional diagrams. A brief description of each logic unit in the standard set is given and the set of peripheral units listed. Mention is made of the design method and the emphasis placed on noise immunity. Constructional techniques and the use of an automatic tester are described. Current assessment of the actual performance of the units is given and future possibilities, including large-scale integration and M.O.S.T. devices, are discussed.