Brake and turn signal adaptor for trailers

DETAILED DESCRIPTION The present invention relates to a new electrical circuit design to adapt the independent turn signal and brake lights on a towing vehicle to the combined turn signal and brake lights on a trailer.
According to one aspect of the invention, the adaptor circuit includes complimentary metal oxide semiconductor (CMOS) exclusive OR integrated circuits (ICs) for providing logic functions in the circuit, and an isolation network comprising a series of LEDs and corresponding phototransistors for preventing feedback to the electrical lighting system of the towing vehicle.
The adaptor circuit is inserted between the electrical lighting system of the towing vehicle and the electrical lighting system of the trailer.
In the isolation network, an LED and corresponding phototransistor are inserted between the brake light connection of the towing vehicle and one input to each of two exclusive OR ICs.
The LED is adapted to be illuminated in response to current flowing to the brake lights in the towing vehicle.
The phototransistor in turn is adapted to produce a logic signal to the exclusive OR ICs when the LED is activated.
The phototransistor thereby provides a high input signal to one input of each exclusive OR IC when the brake light on the towing vehicle is activated.
Similar LEDs and corresponding phototransistors are inserted between the tail light, backup light and right and left turn signal light connections on the towing vehicle, and their corresponding light connections on the trailer.
The exclusive OR ICs in the circuit provide for illuminating both the right and left combined brake and turn signal lights on the trailer when only the brake light on the towing vehicle is illuminated.
Further, the CMOS exclusive OR ICs provide for inactivating the brake signal of the light on the side of the trailer for which the turn signal is operating.
Thus, when the right-hand turn signal light is flashing and the brake light is on, only the left-hand combined turn signal and brake light of the trailer is continuously illuminated and the right-hand combined trailer light is blinking, and vice-versa