Transistor switches for selecting program signals in a wired broadcasting system

Claim 1

A wired broadcasting system comprising a plurality of programme signal sources, and switch means for making a connection between a signal cable extending to a subscriber and any desired one of said programme signal sources, the switch means comprising 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 semi-conductor switch in respect of each operating coil comprising a series of transistors with bases, the subscriber being provided with means for controlling the semi-conductor switches to close any one of the contacts and thereby select a programme signal source, each of the programme signal sources providing a voltage signal which, once that programme signal source has been selected, is applied to the respective semi-conductor switch so as to maintain the selection wherein the base of each transistor in the series is connected to a respective operating coil and the transistor has a circuit arranged such that the respective contacts are closed by its conduction and, once the contacts are closed, the said voltage signal maintains the transistor in its conductive state wherein adjacent transistors in the series are connected by capacitive circuits such that when any transistor in the series is turned off the capacitive circuit connecting it to a subsequent transistor in the series is charged, the charge on the capacitive circuit causing the said subsequent transistor to conduct.