Found in a documentation from the 90s, this circuit limits and amplifies a voice signal in the 800 to 3000 Hz range and is intended for transmission systems.
A narrow range of frequencies around 1 kHz is rejected by the high Q filter shown in the figure,...
This simple converter does not use a transformer and the transistor can be the BD135 for currents up...
This is a circuit from the time when some still called the transistor a crystal triode. It...