This circuit with the CA3059 was found in the July 1995 Elexctronics Now magazine. The signal must be DC, and the circuit is not isolated from the mains.
This adjustable source was found in a 1979 documentation, but all components are still common...
This temperature control was found in General Electric documentation from the 90's. The circuit uses...
This SCR circuit was found in an American 1980s documentation. The circuit is still current,...