"In an embodiment in which the HNM 28 is integrated in a device, such as a set top box and a personal computer, the bus is specific and internal to that device, and the bus-side of the protocol stack includes a device-specific interface for communicating on the bus. [0076] In other embodiments, the HNM 28 operates as a bridge between the backbone 20 and a plurality of local buses of different types" . . . . .