We found this circuit in a Radio Electronics from December 1963. The circuit combines valves and transistors and has a high input resistance. The circuit is powered by two batteries.
This circuit is used in transceivers, enabling input selection by diode switching through polarity...
This configuration was found in an American publication from the 90s. Operators admit equivalents just...
This circuit was found in an Italian magazine Elettronica Prática of 1977. The transistors can be...