https://metrahometheater.com/hdm-sp3.html

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.