Cool circuit... I investigated them all 15 years and discarded them all because they all use too many parts or the quiescent current was too high.. Much too expensive and no protection from electrical discharge or transverse lightning strike. my device operated a latching solenoid with up to 100 meters (tested at 150) of wire. The circuit I finally settled on used 1 DPDT relay, 1 Mosfet, 2 SS transistors, 1 PNP and 1 NPN, a 4700 uF cap and 2 resistors. I replaced ONE relay in 10 years of production of that assembly... and about 5 Mosfets. The same circuit worked well on the 2 coil solenoids as well with one more wire.