This circuit is from an old Japanese publication of 1962. The circuit uses two batteries, one for the filaments of the tubes and the other one of high voltage for the plate circuits.
Found in documentation from the 1970s, this circuit for resistive loads uses a trigger...
This simple receiver for listening on the phone was obtained in a 1960 documentation. The circuit is...
This circuit was found in the 1989 Radio Electronics Experimenter edition. The circuit has the...