This high-Q low-pass filter was found in the October 1990 issue of Radio Electronics magazine. The frequency depends on the capacitors used and is on the order of a few tens of hertz.
This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms...
This circuit shuts off and locks the power to a load in the event of a failure. The circuit is from...
This circuit is from 1995 documentation, but can be easily assembled today, as the components used are...