This circuit produces a pulse when the voltage in the regulator exceeds a certain value depending on the components. PUT is not a common component today. The circuit is from a 1970 EEE.
This circuit with a double-gate MOS transistor was found in a Popular Electronics from the 90's....
This photoelectric cell light relay was found in Radio Electronics magazine from April 1958. The...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...