This circuit was found in a Hands On Electronics from the 80's. The circuit emits an audible alert when dawn and the sensor receives solar illumination.
Two or more 4013 can be cascaded to perform a divide-by-4 (-8, -16, etc.) as shown here. The...
This project from a 1983 publication can be assembled using more modern transistors. We can use...
This circuit is from 2001 documentation with the purpose of controlling a pump that fills a water...