This circuit is from a 1924 book by Gernsback. The receiver uses two tubes and listens to headphones. Power is supplied by battery with the indicated voltages.
This circuit was found in 1980s Radio Electronics. The circuit includes the power supply. The...
This circuit was found in a former Popular Electronics. The timing is set on the potentiometer and the...
This circuit has appeared on our site several times as a battery status monitor. In this...