Found in Motorola's 1967 documentation this circuit can use any general-purpose transistor. The signal should be applied to a good amplifier. The noise diode can be replaced with a common one.
This circuit triggers a warning oscillator if you forget the lights on when you leave the car. The...
We found this circuit in a 1969 General Electric documentation. The circuit uses transistors of the...
This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit...