Abstract @ A communications system comprising a head end, and a plurality of subscriber units each provided with a receiver for receiving transmitted programme signals. A digital signal representative of a message to be delivered to any one subscriber unit is transmitted from the head end. The transmitted digital signal is converted at the subscriber unit to an output signal which can be reproduced as an audible message by the subscriber unit, and the subscriber unit is selectively controlled to reproduce the audible message. The subscriber units may be terminals of a cable television system comprising a trunk cable network connecting the head end to a plurality of switching centres, and a number of subscriber cables connecting the subscriber units to the switching centres. Television signals are transmitted from the head end over a plurality of channels in the trunk network and switched to individual subscribers from the switching centres in response to control signals transmitted to the switching centres from individual subscribers. Signals are transmitted from the head end to contcol the switching centres such that a subscriber's receiver is selectively connected to the channel on which the digital signals are transmitted, whereby audible responses can be transmitted selectively to subscribers.
A communications system comprising a head end, a plurality of subscriber units each provided with a receiver for receiving transmitted programme signals, means at the head end for transmitting a digital signal representative of a message to be delivered to any one subscriber unit, means at each subscriber unit for converting a transmitted digital signal intended for that subscriber unit to an output signal which can be reproduced as an audible message by the subscriber unit, and means for selectively controlling the subscriber unit to reproduce the said output signal, whereby audible responses can be transmitted selectively to subscribers.
Claim 2
Dependent Claim
99 words
A communications system comprising a head end, a plurality of subscriber units each provided with a receiver for receiving transmitted programme signals, means at the head end for transmitting a digital signal representative of a message to be delivered to any one subscriber unit, means at each subscriber unit for converting a transmitted digital signal intended for that subscriber unit to an output signal which can be reproduced as an audible message by the subscriber unit, and means for selectively controlling the subscriber unit to reproduce the said output signal, whereby audible responses can be transmitted selectively to subscribers.
Claim 3
Dependent Claim
123 words
A communications system according to claim 1, comprising a trunk cable network connecting the head end to a plurality of switching centres, and a plurality of subscriber cables connecting the subscriber units to the switching centres, signals transmitted from the head end over a plurality of channels in the trunk network being switched to individual subscriber units from the switching centres in response to control signals transmitted to the switching centres from individual subscribers, wherein means controllable from the head end are provided at the switching centres for selectively connecting the receiver of a subscriber unit to which a message is to be delivered to the channel on which the digital signals are transmitted, whereby audible messages can be transmitted selectively to subscribers.
Claim 4
Dependent Claim
141 words
3 . A communications system according to claim 2, wherein the digital signals are transmitted as teletext and means are provided at the head end for applying teletext signals to that channel, the system further comprising means located at the head end for converting an audio response message into a teletext-type signal forming said digital signal, and means located at the head end for substituting the digital signal for the teletext signal normally transmitted over the said channel and simultaneously transmitting controlling signals to the switching centres to control the connection of the receiver of the or each intended recipient of the message to the said channel, the converting means comprising a teletext decoder for extracting the transmitted digital signal, and an audio signal generator for converting the decoder output to an audio signal which is applied to the receiver loudspeaker.
Claim 5
Dependent Claim
150 words
A communications system according to claim 2, wherein the channel on which the digital signals are transmitted is a teletext channel and means are provided at the head end for applying teletext signals to that channel, the system further comprising means located at the head end for encoding an audio response message as a set of digital instructions suitable for controlling the operation of a speech synthesizer, the digital instructions forming said digital signal, and means located at the head end for substituting the digital signal for the teletext signal normally transmitted over the said channel and simultaneously transmitting controlling signals to the switching centres to control the connection of the receiver of the or each intended recipient of the message to the said channel, the converting means comprising teletext acquisition and storage devices for extracting the transmitted digital signal, and a speech synthesizer responsive to the stored digital signal.
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