This circuit uses three inverters to generate a rectangular signal whose frequency depends on R1 and C1. The circuit is from a March 1996 Electronics Now.
This sophisticated moving bar indicator circuit with the LM3915 is from a Radio Electronics...
This circuit was found in the May 1972 issue of Radio Electronics magazine. The activation code...
This filter for receiving audio in telegraphy was found in a magazine 73 for radio amateurs, in an...