This circuit was obtained from HAM Radio magazine in an 80's issue. The FETs are types of the time and the frequency is determined by the crystal. The circuit operates at voltages from 3 to 9 V.
When light fails to focus on the sensor, a common photo-transistor, the relay closes its contacts....
The component used in this regulator is not common today. The switching circuit is from an 80's...
The basis of this circuit is the 723 integrated circuit, not very common today. We obtained this...