This notch filter was found in National Semiconductor documentation from the 1980s. Operational amplifiers are from that era. The configuration can be adapted to use modern operational amplifiers.
This timer was found in a 1994 Electronics Now. The relay must be a sensitive type. If it has a...
We can make an oscillating relay producing a rectangular signal taking advantage of the inductance of...
This circuit appears at various points in this section and on this site, with minor variations. It uses the...