This old circuit from the 80's generates logic signals with 50% active cycle (squares). The integrated circuit used is not common today, but equivalent logic functions can be used in a modern version.
This circuit was found in a Texas Instruments optoelectronics documentation. The gain depends on...
This oscillator circuit is from a Radio Electronics magazine from September 1960. The frequency depends...
Using a reed relay, this protection circuit depends only on the adjustment of the closing point by a wire...