These compact devices maintain the Ethernet/FastEthernet or up to Gigabit Ethernet (SP427A) communication across an electrical isolation barrier. They protect the equipment on one segment from being harmed by damaging surges and power anomalies on another segment. Install them in-line. The devices draw their power from the network and connected equipment. So there is no need for an extra power supply. Whatsmore meeting the EN6060-1 standard, they can even be used in medical applications.