WIRED BROADCASTING SYSTEMS

摘要

1,272,594. Wired broadcasting systems. COMMUNICATIONS PATENTS Ltd. 5 Aug., 1969 [9 Aug., 1968], No. 38108/68. Heading H4R. In a wired broadcasting system each subscriber is connected to a programme exchange by a respective feeder cable Fig. 2 having a twisted pair of insulated conductors 14, 15, to convey signals from the programme exchange to the subscriber, and a pair of control conductors 16, 17, to carry control signals from the subscriber to the exchange. The control conductors are arranged in the interstices formed between the pair of signal conductors and convey to the exchange programme selection signals, pay programme acceptance signals, and audience response signals if required. Fig. 4 shows an embodiment of a system in which a programme exchange, 24, is fed with vision signals of three programmes on coaxial lines 25, 26 and 27 and audio signals on pairs 28, 29 and 30. The vision and corresponding audio signals are combined on respective trunks 34, 35 and 36, which are connected to the programme selector switches, such as 37, of which one is provided for each subscriber. The selector switch is positioned by an electromagnetic driving device 38 under the control of signals received from the subscriber over the control pair 46 while the selected programme is transmitted to the subscriber over the signal pair 43 via a balun transformer 39 and a pay programme lock-out switch 41. Also transmitted over the signal pair 43 is a charge signal which operates an indicator 44 at the subscribers station to indicate the programme price and acceptance of the charge is indicated by the subscriber by connecting a tone generator 47 to the control line which signal unlocks the lockout switch 41 and registers the appropriate price on the pay meter 50. In order to assess programme popularity a constant voltage supply 52 is connected to each programme trunk line and each subscriber has a load 56 which draws a predetermined current from the trunk line to which it is connected, so that the programme popularity may be measured by the current meter 53, 54 or 55, through which the supply 52 is connected to the trunk lines. In addition the programmes selected by a particular subscriber may be recorded on meters 59 to 61 connected via a switch 57, coupled to the programme selector switch, to a power supply 58. A further tone generator 62 is provided at the subscribers station in order to provide audience response signalling over the control line.