Found in an old English publication, this circuit applies to the 240 V network, but can be changed to lower voltages. Transistors are mostly general-purpose, admitting modern equivalents.
This space mark demodulator for FSK signals was found in an American telecommunication...
This one transistor stage for audio signals was found in an old publication of the year 1958. The...
This audio step operates directly with the 110 V mains voltage rectified and reduced. The output...