This circuit indicates when a rain is acidic by monitoring its pH. The circuit is from a 90s RE Experimenter Handbook. Some components used can be difficult to obtain today.
Based on Allegro's A6275, this circuit controls the brightness of various displays. The circuit is valid...
This small transmitter can act as a wireless microphone operating in the medium wave range,...
This is the circuit of an RCA Dimmer sold in 1967. With it it is possible to control a load up to...