Abstract: A wired broadcasting system in which subscribers are connected to a program exchange through their own individual pairs of twisted conductors. Each pair is associated with an intersticial pair of conductors for low frequency signals.Central information processing equipment is provided functionally connected to the subscribers' stations to permit collection of data at the central processing station. Coded signal data is sent from the central processing station via the program exchange to the subscriber stations, local data is introduced into the coded signal data at the subscriber station, and the supplemented coded signal data is returned to the central processing station.

Abstract: A switch is disclosed which comprises a pair of diodes connected in series with opposed polarities, and a solid state device for applying potentials to the connection between the diodes to render the diodes either conductive or non-conductive. The switch may be used in a wired broadcasting system to connect a subscriber to a program source.

Abstract: A wired broadcasting system is disclosed in which a plurality of subscriber units are connected to a program exchange at which a plurality of program signals are made available by respective cables. A program selector is provided in respect of each subscriber unit and the subscriber unit is able to control the respective selector. At least one secondary program signal source is provided at the exchange and at least one subscriber unit is provided with control means for controlling the application of program signals from the secondary program source to the respective cable.

Abstract: A wired broadcasting system is described which comprises a plurality of program signal sources, and a switch for making a connection between a signal cable extending to a subscriber and any desired one of said program signal sources. The switch comprises a plurality of electro-magnetically operable contacts connected between respective ones of the signal sources and the signal cable, an operating coil in respect of each contact, and a semiconductor switch in respect of each operating coil. The subscriber controls the semiconductor switches to close any one of the contacts and thereby select a program signal source. Each of the program signal sources provides a voltage signal which, once that program signal source has been selected, is applied to the respective semi-conductor switch so as to maintain the selection.