This alarm circuit was found in April 1975 Radio Electronics magazine. The circuit uses a 12 V power supply and relay but can be modified to work with other voltages.
This simple MW radio was found in a 1975 publication, but it can be mounted with BC548...
This control for bass, midrange, and treble was found in the March 1995 issue of Electronics Now...
This circuit from a 1967 documentation generates 2.5 Hz signals depending on the capacitors used,...