Abstract: A control for activating an electrical load, such as a lighting system, in a motor vehicle having an ignition system. A first voltage, inversely proportional to the frequency of the motor vehicle ignition pulses, is applied to the anode of a programmable unijunction transistor (PUT), and a fixed reference voltage is applied to the gate of the PUT. At low engine speeds, the PUT tends to conduct periodically, deactivating a relay which is operable to energize the motor vehicle headlights. At higher engine speeds, with a greater frequency of ignition pulses, the programmable unijunction transistor fires less frequently, or not at all, allowing the energization of the headlight relay and hence, the application of power to the headlights. Circuitry is also provided to energize the motor vehicle headlights, taillights and instrument lights in response to the activation of the motor vehicle windshield wiper motor and also in response to ambient darkness.

Abstract: A control for activating an electrical load, such as a lighting system, in a motor vehicle having an ignition system. A first voltage, inversely proportional to the frequency of the motor vehicle ignition pulses, is applied to the anode of a programmable unijunction transistor (PUT), and a fixed reference voltage is applied to the gate of the PUT. At low engine speeds, the PUT tends to conduct periodically, deactivating a relay which is operable to energize the motor vehicle headlights. At higher engine speeds, with a greater frequency of ignition pulses, the programmable unijunction transistor fires less frequently, or not at all, allowing the energization of the headlight relay and hence, the application of power to the headlights. Circuitry is also provided to energize the motor vehicle headlights, taillights and instrument lights in response to the activation of the motor vehicle windshield wiper motor and also in response to ambient darkness.