Found in an American circuit manual from the 1970s, this circuit can use any general-purpose transistor. The operating frequency range is from 600 to 4000 Hz.
This circuit for conventional lines was obtained in a 1996 documentation. The circuit uses common...
This tube circuit was found in the magazine 73 for radio amateurs in an issue from the 1980s. Note...
September 2016 - can already be found at Mouser Electronics new integrated circuit from Texas...