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 is from the SGS manual of linear integrated circuits of 1982. The L78xx is equivalent to...
This low displacement circuit was found in American documentation from the 90s. Operational...
The purpose of this circuit is to maintain the liquid level of a reservoir between two values...