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.
In the figure we have an amplifier step configuration with a transistor suggested by a 1985...
This small telegraph transmitter has a range of a few meters, operating at a frequency that...
This circuit is from an old documentation. Integrated circuit 723 is not common today. The power...