The HDM-SP3 was designed to clamp ESD spikes up to 8000 volts (IEC 61000) down all channels including the TMDS and DDC lines. This will provide excellent protection from the ESD spikes that enter your systems through any of the data ports (Coax, Ethernet and Serial), usually from your CATV/Internet provider. What the HDM-SP3 does not protect you from, direct lightning strikes, sorry but this is well beyond 8000 volts. Minor over-voltage, this is sadly something that we are seeing a lot more of and it is not a spike or surge. It is instead a constant feed of too much voltage that is passed onto the HDMI feeds and eventually wears out the HDMI ports downstream. Think of it as being subject to a constant barrage of (very) loud music that you do not even like. ESD Electrostatic discharge is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short or dielectric breakdown.