At one campground I kept getting low voltages on my PI EMS. Campground was sure the problem was the EMS. Called PI and they gave me an easy test to detgermine if the EMS was working properly. Started the generator and when the coach was on Gen power, ran an extention cord from a coach receptacle and plugged the SP cable into the extension cord via a 50-30 pigtail to a 30-20 plug. Low and belod the EMS was dead on - 120VAC @ 60hz. I now run this test to verify if the generator is working correctly. Most of use don't carry a freqmeter - the EMS has a built in frequency detector. By the way, we left that campground in RI never to return. JM2ยข...