The Standard provides symbols@ both basic and non-basic@ for binary operating functions. The use of symbols in typical systems is illustrated in appendices. The Standard is intended to symbolize the binary operating functions of a system in a manner that can be applied to any class of hardware@ whether it be electronic@ electrical@ fluidic@ pneumatic@ hydraulic@ mechanical@ manual@ optical@ or other. Purpose The purpose of this Standard is to provide a method of logic diagramming of binary interlock and sequencing systems for the startup@ operation@ alarm@ and shutdown of equipment and processes in the chemical@ petroleum@ power generation@ air conditioning@ metal refining@ and numerous other industries. The Standard is intended to facilitate the understanding of the operation of binary systems@ and to improve communications among technical@ management@ design@ operating@ and maintenance personnel concerned with the systems.