Found in a Popular Electronics from the 90s, this circuit uses common components with several operational options, including the use of an optocoupler that allows its application in a shield.
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...