This circuit was found in documentation for radio amateurs of the 1980s. The circuit is intended to produce a tone for modulation in telegraphic transmissions.
This power source, obtained in a 1973 publication, suggests the use of partially burned germanium...
This circuit was obtained from an Electronic Design from 1964. Transistors admit modern...
The circuit is from the 1994 National Semiconductor Linear Applications Handbook but can be...