Found in na 1969 Electronics World, this circuit makes use of transistors of the time. Equivalent transistors can be used. The diodes can be 1N4004.
In the original 1992 application, this passive circuit was intended for use in the car. At that...
This 1995 circuit uses an audio amplifier that is no longer common today. However, other...
This circuit is from an 80's documentation. The integrated circuit is from the time and the...