Logic gate circuit to close when sensor signal turns ON and then OFF, but must ignore another ON?

Question

I am trying to put a permanent magnet in a transformer between both coils, so that the transformer can utilize the flux from the permanent magnet by guiding its flux periodically.

We have one primary coil that will change the direction of the flux from permanent magnet towards the other secondary coils one by one. I want primary coil to change polarity when the first secondary coil rate of change of flux becomes zero.

So I'll put a reed switch to detect the magnetic field that causes inducing of voltage into secondary coil. I want another switch named switch A to turn ON, when reed switch turns OFF after turning ON, but when the same reed switch turns ON (and OFF) again (on collapsing the magnetic field in secondary coil) the switch A should do nothing. And then how would I reset the reed switch to detect the change in magnetic field again?

Timing diagram (edited on request).

              __    __    __    __    __    __    __    __    __
    Reed  ___|  |__|  |__|  |__|  |__|  |__|  |__|  |__|  |__|  |__

                 __          __          __          __          __
Switch A  ______|  |________|  |________|  |________|  |________|

I couldn't find it on internet, can somebody please draw the circuit to achieve the same?

Answer 1

Here's the logic.

And here's the timing diagram.

Relay 'A' would set and reset on alternate pulses of the reed switch.