The uses of this circuit are the most varied. From place in the front door to prevent people stop in front of it without even placing it in the back and front of the car to warn other drivers when they get too close to the park. Circuit operation is based on a burst emit infrared light signals which the bounce on a near object are received by another component. To be received by the system detects the proximity to the LED output is activated (flashing). The integrated circuit is a generator / tone decoder that well meets the needs of this design. Both the photodiode and the phototransistor should be located with units suitable approach to improve the range. With simple LED spotlights are available scope of the order of meters. Convex lens can cover distances of five meters. It should sacrifice some range but SUNLIGHT put UV filters and which are not allowed in the phototransistor (receiver element) rays from the sun. Feeding this circuit can be any voltage between 5 and 9 volts. External circuitry for driving the LED is sufficient to replace by an optocoupler, which actuated by means of its internal transistor circuit to be controlled.