Using 4 tubes, this 1924 receiver combines new technologies as an intermediate frequency stage that was already beginning to appear. Listening is via phone and battery power.
Found in an EEE this circuit uses FETs of the time and a bipolar one. Current equivalent...
This capacitive switch or approximation relay was found in a 1980s US publication. Power should...
Although it is a common configuration today, this circuit was taken from an old publication. The...