RF or even switching transistors like the 2N2222 can be used in this circuit. The capacitors are ceramic and the frequency is determined by the crystal.
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...