With this circuit, signals in the range of 10 kHz to 150 kHz can be received at close to 4 MHz from a shortwave receiver. The circuit is from a 303 Circuits from the 90s.
This timer, from an old American publication, uses indicator lamps, but can be modified to use...
This didactic circuit from a 1977 Radio Shack documentation shows how to use the 741 as a...
Found in an 80's Hands On Electronics, this circuit turns on a light when it gets dark and goes...