Found in an old Popular Electronics this circuit appears in other variations on this site and in this section. It uses a 7-segment common anode LED display as an indicator.
This first order Butterworth filter is tuned to frequencies around 1 kHz. The frequency is given...
This very low current circuit was found in the April 1995 Electronics Now magazine. The frequency...
This circuit was found in an American 1980s documentation. It makes use of an unusual MOSFET today...