PURPOSE: To facilitate the connection to controlled machine and the supply of checking input signal for the machine, by individually providing switches at input terminals on a printed circuit board.

CONSTITUTION: Toggle-type switches 8 corresponding to terminals 7 are attached to the printed circuit board 6 having desired electric circuits made by pattern printing on its obverse and reverse sides. One electrode of each switch 8 is coupled to the corredponding terminal 7 and the other electrodes of the switches 8 are short-circuited to one another and coupled to a common terminal 9. The terminals 7 are mounted on input terminals 3 on a sequence unit and a checking input device 5 is installed. Thereby, the switches 8 are connected to the input terminals 3, respectively, and the common terminals 9 is connected to another common terminal 4. A desired checking input signal is applied to an input terminal 3 by operating the lever of the corredponding switch 8