This circuit is from 1964 documentation but can be easily implemented based on current components. Input waveforms and detection are shown next to the diagram.
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...