This circuit was found in an article in Electronics Now magazine from March 1997. The transistors are general purpose, and the indicator is a 1 mA full scale analog type.
This circuit came out in an English publication of 1976, but it can be easily assembled using...
When light fails to focus on the sensor, a common photo-transistor, the relay closes its contacts....
This traditional clock circuit with common CMOS components with discrete logic functions was found...