Abstract: A warning device for use on a vehicle for sensing an approaching object when the vehicle is moving backward. The device produces a first signal when the object is in remote proximity of the vehicle and at least a second signal when the object is in close proximity of the vehicle. The device has a circuit for emitting intermittent infrared light when the vehicle is moving backward and a circuit for receiving the infrared light reflected from the object. The circuit for receiving produces a receive signal indicative of the received infrared light. The device further has an output of the circuit for receiving connected to two inverting inputs of both first and second differential amplifiers, inverting inputs of the first and second differential amplifiers being connected by a first and second variable resistors, respectively, to an applied voltage. First and second outputs of the first and second differential amplifiers, respectively, are connected to first and second inputs of an AND gate.