The TP-POE-1824G Power Over Ethernet 802.3af/at converter is a unique product
allowing a customer to run a Passive PoE device from a standard 802.3af or at
PoE switch. They accept 802.3af/at PoE in and provide a switch selectable 24W
PoE output of 18VDC or 24VDC.
They work by supplying power to the remote device on the unused Ethernet pins
4,5(V+) and 7,8(V-). The Ethernet spec supports distances up to 100m (328 feet).