Patent US 5,463,619

A local communication bus system including a serial control bus connected to a plurality of user terminal devices and at least one switchbox device, each terminal device being plug connected to at least one of the switchbox devices so as to provide respective signal interconnection paths there-between, each device having at least one plug and containing a readable interconnection table specifying to which plugs of other devices it is connected. A signal path from a terminal device operating as a signal source to a terminal operating as a signal destination is established by control commands generated on the connection bus by a control unit in the source device and which cause the intervening switchboxes to establish the requisite internal connections between their plugs. The system thereby does not require any central control. The interconnection table of a terminal device only needs to identify its own plugs and those of other devices to which it is plug are connected.