A main control circuit for controlling a door open-close drive motor and a lamp illuminating the interior of a garage is disposed in a body of a door operation control apparatus, and an interface circuit for applying control command signals to the main control circuit is connected by two signal conductors to a control box mounted on the wall of the garage. Signal voltages of a plurality of levels can be generated from the control box to be transmitted to the interface circuit by way of the two signal conductors, and the interface circuit discriminates the level of one of the signal voltage transmitted by way of the two signal conductors to apply a control command signal for controlling a controlled object corresponding to the discriminated voltage level.