Abstract: A programmable controller comprises an input circuit including a plurality of signal input terminals which receive signals from a plurality of external input devices, and a power feed terminal and a ground terminal which are respectively exposed in order to supply a power source voltage from outside the programmable controller. Also, current regulator elements are respectively located between the power feed terminal or the ground terminal and the plurality of signal input terminals. Owing to this construction, the range of power source voltages to be supplied to the input circuit can be widened, and various external input devices can be connected without altering internal circuitry. A plurality of power sources of fixed voltages which are generally used are built in, whereby a user need not especially prepare a power source and can be freed from the labors of wiring etc.