We found this circuit in the May 1989 Radio Electronics magazine. The circuit can have its values changed to operate at other frequencies and the power supply must be symmetrical.
This circuit warns when the headlight bulb is on. We found it in a Popular Electronics from the...
The oscillator shown in the figure keeps its frequency constant in an active cycle adjustment...
This circuit was found in an Argentine publication from the 1970s. The circuit can be assembled with...