Title is AC reverse polarity phase detect circuit for boat power I have a boat The boat has a reverse phase polarity circuit using an alarm and light. The new rule is a 25000 ohm impedance resistance must be maintained between neutral and ground wires. The current old alarm has 0.5k resistance. I also want to power a SPDT 12 vdc relay to turn my 4 pole 35 amp main disconnect relay off and on. So that power to the boat is turned off and the alarm sounds if power exists between neutral and the ground wires due to reversed polarity phase condition. I can do it all myself using a relay etc... BUT the circuit will have a low resistance like 300 ohms not anywhere near the 25,000 ohm rule. So what can I do? Can anyone show a circuit that can maintain that high 25,000 ohm impedance and still allow switching a relay and turning on the alarm? Here is pic of alarm. Pic of relays before being wired up and more info on what I am talking about here http://www.oceannavigator.com/January-February-2003/Wiring-a-reverse-polarity-alarm/ http://www.jamestowndistributors.com/userportal/document.do?docId=91 I have a functional light as described in article. The other problem with joining neutral to ground on a boat is power may flow from ground wire through your body back to the source. Especially if the ground wire at the shore plug breaks.