Provides total electrical protection of RV electronics and complete digital readout of the AC power source. Protects against high/low voltage problems, incorrect AC wiring, and power surges, while the built in display continually scrolls, showing line voltage, current, frequency, and error message. EMS shuts down power if AC source drops below 104V or rises above 132V, automatically restores it once power is between 104V-132V after 136 second delay. Power is also shut down if AC outlet is wired incorrectly, or 220V is detected on the 120V power line(s). The error message notes AC power condition. 30 amp models have surge rating of 450 joules and 3-mode protection, 50 amp models have 750 joules, and 4-mode protection. Surge light denotes condition of surge circuit. Portables models are weather resistant, and have a built-in theft device. Hardwired models include remote digital display and hardware. 3 year Warranty.