Power over Ethernet or PoE describes a standardized system to pass electrical power along with data on Ethernet cabling. This allows a single cable to provide both data connection and electrical power to such devices as network hubs or closed-circuit TV cameras. Unlike standards such as Universal Serial Bus which also power devices over the data cables, PoE allows long cable lengths. Extra pairs of wire, not used for data transmission, are used for power. Up to 25 watts is available for a device, depending on the version of the standard in use. Numerous non-standard schemes had been used prior to PoE standardization to provide power over Ethernet cabling. Some are still in active use.