US Patent 7132927 Universal serial bus extension cable

A controller capable of being located in a peripheral device or host, is capable of engaging in data communications with a host or peripheral device over a power line. A power line interface provides a first data communications interface over the power line. An interface controller connects peripheral device and host using the first and a second data communications interface having a protocol. A power supply supplies power associated with the second interface. The controller appears to the peripheral device as the host or as the host to the peripheral. In accordance with the protocol the power supply supplies power such that the interface is fully compliant with the protocol.