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 circuit triggers an alarm in the event of a power failure. The circuit is from an 80's...
We found this circuit in the April 1978 issue of Radio Electronics magazine. The 2-digit circuit uses...
This CMNOS crystal-based circuit generates a 2 Hz signal. It was found in the October 1994 issue of...