Indicated for powering circuits with operational amplifiers, this source was found in Popular Electronics. The output voltage depends on the transformer used, as well as the current.
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...