Found in a Popular Electronics from the 90's, this circuit can generate frequencies according to the values of the employed components, according to the table next to the diagram.
This circuit has an LED indication of the timing progress, having been found in an old...
This circuit is from a Radio Electronics magazine from August 1974. It used one of the first...
This charger is powered by the car's 12 V socket, the number of diodes being calculated according to...