be a back up rechargeable battery coupled with it not shown the overload circuitry 61 contains a germanium diode 54 combined with heater 55 resistive for instance connected into the circuit of a motor 15 supply and coupled with transistors 48 49 with adjustable resistor 49 a which determines the threshold voltage depending on the temperature of the diode at which the transistors become closed see fig9 when the sensor 47 provides an output impulse of duration delta t which may be pre set in the case of a paradoor u2122 460 sensor the relay 62 is energized and the current is directed to motor 15 through the coil of the heater 55 and normally closed micro switch 59 27 the arm starts its swinging movement and upon reaching the end limit disconnects the current through the motor 15 by micro switch 59 27 as soon as the arm starts its movement the switch 60 28 which is normally open closes when the output impulse from the sensor 47 expires the coil 56 is de energized and the relay returns to its normal configuration this causes the motor 15 to reverse its direction and the arm 4 returns in retracted position the switch 60 28 opens and the motor stops when the door is being closed activation of the sensor 47 will provide for immediate reversal of the motor 15 and the door opening if the door is open and sensor 47 detects the presence of another person in a door way the door will remain open which will allow to eliminate overworking of the.