We found this circuit in a 1996 publication. The circuit uses components that are still common. The timing depends on C1, which can be changed, and the triac can be of any type.
The ZN416E integrated circuit is uncommon today. It consists of a complete radio, like the one...
This circuit is from an English magazine of 1977. The circuit is still current, just using a TIP41...
This two-tone alarm siren was found in the January 1975 issue of Radio Electronics magazine. The...