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Programmable controllers, or P.C.s, have been used in industry in one form or another for the past fifteen years. The newest models may not resemble their earlier counterparts, but many of the concepts used in the first units are still in use. The programmable controller is basically a computer-controlled system containing a microprocessor that is programmed with a programming panel, or keyboard. The P.C. is dedicated to receiving input signals and sending output signals in response to the program logic. The program generally consists of contacts, outputs, timers, counters, and math functions. The programmable controllers found in industry today have evolved from the need for a control system that can be easily reprogrammed as changes occur or as new products develop. For example, the automotive industry is faced