ETA-S20, noise filtering for unwanted radio frequency interference (RFI) that commonly introduced into AC lines by nearby radio transmitters or wireless products. EMI filters are also incorporated to reduce noise from electromagnetic interference (EMI) generated by items such as electric motors and switching power supplies. Unstable AC mains voltage is one of main reasons for equipment failure. Amount of energy that can be injected into power system can be immense with voltages reaching 6kV or amperage peaks of 3000A. Spikes are very fast and usually only last for very short period of time. ETA-S20's circuitry very fast and can suppress unwanted energy within a nanosecond response and sustain the suppression up to 2 milliseconds.