This 1/2 hertz high selectivity filter was found in the December 1990 issue of Radio Electronics magazine. The source must be symmetrical. The capacitors can be changed for other frequencies.
This is the basic configuration of a monostable TTL with the 74121. The trip is done with an NC...
This fixed source configuration with 78xx series regulators has already been explored in several...
In the figure we have a TTL logic interfacing circuit as CMOS logic using a 6N139 optocoupler...