Progressive Industries Portable Electrical Management Systems (EMS) provide full RV protection against all adverse power conditions. You will feel secure with multi-mode surge, voltage, polarity and lost/open neutral protection. Each unit includes a digital display, scrolling continuously through the power source information: Voltage(s), current, frequency, error code, and previous error code (if applicable). Replacement parts are simply plug-and-play, making repairs quick and easy. As with our portable models, the computer is driven by state of the art microprocessors. Should the software ever change, EMS owners can receive a free upgrade at no cost.