These are individual Power over Ethernet power injectors. See photos of specifications on base of unit. They have a standard computer IEC type ' kettle' power socket and therefore can be attached to the mains power via a standard lead.This lead is not included (standard lead) Each injector also has an Ethernet RJ45 10/100 Data Input Socket for a standard network cable. Plus an Ethernet RJ45 10 /100 Data and Power Output socket for a standard network cable. The idea is to power a POE compatible remote device such as a ceiling access point or a wall camera etc. It provides POE standard 48 Volt power at 420mA. These are highly effective switch mode devices, built to a very high spec. They have been used successfully with Draytek AP800 series wireless access points and similar. They greatly simplify installation allowing just a single, low voltage ethernet cable to connect and power a compatible network device in a difficult to reach location where there is no nearby 240 Volt mains socket. A Webcam at thh top of a pole in an external enclosure has been suggested for a further application. Dimensions - 11cm x 7 cm x 4 cm max with rubber feet. Green power on LED. Colour black. Indoor use only, typically in comms cabinet or next to router.