PURPOSE: To send an emergency stop signal even for a device having wooden structure and ensure safety in the case of disconnection of electric wire.

CONSTITUTION: The opening and closing of a normally-opened switch 11 and a normally-closed switch 12 of an emergency stop switch 10 are detected by an emergency circuit 13 to output an emergency stop signal S so as to detect the opening and closing of the normally-opened switch 11 and the normally- closed switch 12. The presence or absence of the emergency stop signal S outputted from the emergency circuit 13 is detected by disconnection circuits 14, 15 to output a disconnection detection signal G.