We found this circuit in a 1968 Electronics World. It fires a buzzer if the ignition key is turned on and the headlight is off. The circuit uses an included oscillator buzzer like the Sonalert.
This circuit is from an Electronics Now from August 1995. The triac is according to the load that...
Although it was found in a British magazine 1976, this circuit can be easily upgraded with the...
This circuit was found in the January 1992 issue of Radio Electronics magazine. The capacitor...