This circuit, which controls both the temperature and the level of a liquid in a reservoir, was found in an Electronic Design from the 90s. The circuit is based on a double 555.
This good gain antenna up to 30 MHz was found in an American 1990s documentation. The circuit can be...
This circuit keeps an LED on briefly when S1 is pressed. The time depends on C1. The circuit is...
This circuit was found in the September 1992 issue of Radio Electronics magazine. The circuit does...