This circuit, from a 303 Circuits from the 90s, uses a telephone pickup coil as a sensor to capture power grid noise, thus making it possible to locate electrical wiring.
This circuit was found in the October 1989 issue of Radio Electronics magazine. It drives an...
This interesting configuration was found in a 1965s Electronic Design. It makes use of components of...
This interesting bandpass filter using an operational amplifier 741 has its cutoff frequency...