Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the Sonalert type with included oscillator.
TDK provides a wide range of EPCOS varistors for surge protection through Mouser Electronics....
This excellent preamp for use with guitars was found in a 1986 documentation. The key on the TR2...
This complete experimental source of low current and very high voltage can generate voltages from...