PURPOSE: To detect surely the press contacting and separating condition of a developing roll, pressing roll and developing soln. feed roll by controlling the speed of a means for driving a copying machine at a prescribed speed irrespectively of the set printing speed of the copying machine in the stage of starting and stopping said machine.

CONSTITUTION: When the operator pushes interlocked operating switches 50, 52, a power source is turned on to a copying machine and a switch 80 turns on and a switch 86 turns off. The conducting period of the square wave of a comparator 90 is specified by the prescribed DC voltage divided by resistors 82, 84 and therefore the rotating speed of a motor 96 attains a prescribed speed and three rolls contact surely with each other under pressure. A microswitch 32 turns on at this point of time and the rotation of the driving motor is in a normal state. When the operator turns off the power source to the copying machine by pushing a switch 98, a cam shaft 32 rotates at the preset rotating speed. The microswitch 32 is then turned off to stop the copying machine. The press contacting and separating state of the three rolls is thus surely detected.