This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and the coil can be made with 80 to 100 turns of fine enameled wire on a ferrite rod.
This circuit was obtained in a 1969 documentation. The circuit modulates both the emitter current and...
This source can supply currents up to 5 A and the transistors admit equivalents such as TIP32. The...
This circuit was obtained from an English magazine from 1980, but as it uses components that can...