We found this circuit in a 1957 Raytheon transistor publication. The circuit can be assembled with more modern transistors with minor changes. The handset must be high impedance magnetic.
We found this circuit in a 90s 73 magazine for radio amateurs. The circuit has 3 W of power and can...
This circuit is from old American documentation, but the transistor used is still very common...
This circuit uses a simple power source, having been found in the Philips Databook of 1990....