We found this circuit with the LM3914 IC in a Radio Electronics magazine from June 1985. The circuit is intended for monitoring the battery voltage through an LED bar.
With the components indicated, the circuit oscillates at 20 MHz. The coils and capacitors can be...
The trigger shown in the figure, built around a 4093 can generate pulses that reach 1 hour with a...
This circuit was obtained in an old American documentation, remembering that the 566 is the double...