This alarm circuit was found in the July 1992 Radio Electronics magazine. The circuit uses a small power stage for the speaker and has the sensitivity adjustment at R5.
Found in old documentation about neon lamps, this circuit shows how to add a simple blown fuse...
This charger for automotive use provides a 0.42 A output current. We find it in an American...
This circuit was found in a 1965 General Electric documentation. SCRs and unijunction may be...