This circuit is from a 1968 Electronics World. It acts directly on a high voltage alternating current relay. The sensor can be a common LDR.
Found in the July 1968 Supertena Bulletin of a Popular Electronics, this receiver makes use of the...
This switching source was obtained in a 1976 National Semiconductor manual. For the indicated...
This configuration appears several times on this site. The circuit can generate a 100 kHz or other...