Abstract: A USB extension system is disclosed which converts the standard USB signal into a low voltage differential signal and is installed between a USB hub or host and a USB device, and which drives the interconnecting cable with a true differential signal, i.e. a balanced signal, the problems with interference are greatly reduced. In accordance with the present invention, the standard USB signals are encoded into differential form using differential signals of different magnitudes. In one embodiment, differential signals of a “weak” magnitude are used to encode the “J” and the “K” states of the standard USB protocol, and differential signals of a “strong” magnitude are used to encode the standard “EOP” (End of Packet) USB state.

Abstract: A multi-user computer system using a communications protocol in transmitting data between a plurality of user interface units is described. The system includes a base unit, which has a bus, a processor coupled to the bus, a display device coupled to the bus, an input device also coupled to the bus, and an interface controller coupled to the bus, wherein said processor controls the operation of the base unit and processes data entered into the base unit and operates to generate output data to be displayed on the display device. The system also includes an auxiliary unit, which has a protocol interface controller, a second display device coupled to the protocol interface controller, a second input device coupled to the protocol interface controller, wherein the protocol interface controller controls the operation of the auxiliary unit and interface with the base unit in accordance with a predetermined communications protocol.