This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
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...