The 30 Amp Surge Guard portable with LCD display offers more than twice the Joules of power surge protection than the previous model. Continuously monitors for voltage and amp draw and reverse polarity (miswired pedestal, elevated ground voltage). Compact and easy to use, they plug in between the power pedestal and the line cord to provide protection. Designed for all travel trailers, 5th wheels and motorhomes with 30 Amp service.