This circuit was obtained in an American publication of the time. Transistors are commonly used. The circuit can be adapted for use as a shield.
This circuit is from a Radio Electronics from March 1970. The crystal depends on the frequency at which...
This circuit was found in a 1960 transistor manual from Sylvania. It measures the intensity of...
This audio mixer was found in an old American documentation. The potentiometers are 1M and the...