The 802.3af/802.at PoE (Power over Ethernet) Tester, connected to an RJ45 outlet, allows one to test the live Ethernet cable and determine if power and data are present. And also identifies the type of Power Sourcing Equipment (Either Endspan or Midspan) in your network. This unit is an easy-to-use Power over Ethernet adapter for professionals, business and home users to determine the existence of PoE.