Latching mosfets used so each of the momentary switches doesn't do anything until the previous switch has primed it. If the power is dissconnected or turned off with the latching switch, then the whole circuit resets and the sequence has to be started again.
Relays are used in the last instance to isolate the load from the power supply and ignore any resistance if the mosfets don't saturate. But could also be used to provide AC mains power.
