A two-way cable television broadcasting system wherein a single coaxial cable is used to deliver TV and FM programs to many subscribers with each subscriber having a specific allocated band of frequencies for reception of any desired television or FM program and where each subscriber can independently select the program desired to be seen and/or heard which will be delivered to the subscriber over an allocated band of frequencies. The subscriber drops from said coaxial cable are so arranged that they descend in frequency along the length of the feeder cable. Automatic switching of any incoming program to any drop is achieved by means of converting all incoming channels to a common I.F. frequency at an amplifier or control station and then deconverting said frequency to the desired outgoing band of frequencies.
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1. In a cable distribution system having a head end, means at said heat head end for receiving multiple television channels, a coaxial cable having multiple channel capacity connected to said head end, a bridger amplifier connected to the coaxial cable for receiving and amplifying signals in the multiple television channels, a control station connected to the bridger amplifier, said control station including a switching network and channel converters connected to the bridger amplifier, a feeder cable having a plurality of subscriber allocated channels, said feeder cable connected to the switching network and channel converters, a plurality of subscriber drops connected to the feeder cable, each subscriber drop being connected to a single subscriber allocated channel in the feeder cable, thereby allocating one channel in the feeder cable to each subscriber drop, means at each subscriber drop for sending a control signal to the control station on the subscriber allocated channel allocated to that subscriber drop to control the switching network at the control station.
12. A cable distribution system having a head end, means at said head end for receiving multiple bands of frequencies, a coaxial cable having capacity for multiple bands of frequencies connected to said head end, a bridger amplifier connected to the coaxial cable for receiving and amplifying signals in the multiple bands of frequencies, a control station connected to the bridger amplifier, said control station including a switching network and frequency converters connected to the bridger amplifier, a feeder cable having a plurality of subscriber allocated bands of frequencies, said feeder cable connected to the switching network and frequency converters, a plurality of subscriber drops connected to the feeder cable, each subscriber drop being connected to a single subscriber allocated band of frequencies in the feeder cable, thereby allocating one band of frequencies in the feeder cable to each subscriber drop, means at each subscriber drop for sending a control signal to the control station on the subscriber allocated band of frequencies allocated to that subscriber drop to control the switching network at the control station.
2. In a system set forth in
3. In a system as set forth in
4. In a system as set forth in
5. The cable distribution system of
subscribers on request. 7. In a cable distribution system having a head end, means at said head end for receiving multiple channels, a coaxial cable having multiple channel capacity connected to said head end, a bridger amplifier connected to the coaxial cable for receiving and amplifying signals in the multiple channels, a control station connected to the bridger amplifier, said control station including a switching network and channel converters connected to the bridger amplifier, a feeder cable having a plurality of subscriber allocated channels, said feeder cable connected to the switching network and channel converters, a plurality of subscriber drops connected to the feeder cable, each subscriber drop being connected to a single subscriber allocated channel in the feeder cable, thereby allocating one channel in the feeder cable to each subscriber drop, means at each subscriber drop for sending a control signal to the control station on the subscriber allocated channel allocated to that subscriber drop to control the switching network at the control station. 8. In a system set forth in claim 7, wherein the allocated channel frequencies are allocated to subscriber drops in a descending order depending on the distance of such subscriber drop from the control station. 9. In a system as set forth in claim 7, wherein the switching network controls programs from multiple channel sources such a libraries and schools which are sent to each subscriber on his allocated channel for reception of desired programs. 10. The cable distribution system of
13. A system set forth in
14. A system as set forth in
15. A system as set forth in
16. A system as set forth in
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In the following detailed description and the drawing, like reference characters indicate like parts.
In FIG. 1 is shown a Trunk and Bridger Amplifier and Control Station where the Control Station 1 receives signals from the bridger amplifier 2 and sends them to the subscribers. It also receives signals from subscribers and sends them upstream to the cable system headend by way of the Return Trunk Amplifier 3.
In FIG. 2 is shown a Control Station 1 and a feeder cable 10, descending from said Control Station. The closest subscriber 4 is allocated the TV channel spectrum of 294-300 MHz plus the FM spectrum 88-108 MHz and the most distant subscriber 5 is allocated the TV channel spectrum 54-60 MHz plus the FM spectrum of 88-108 MHz. The other subscribers on the feeder cable are assigned TV channel spectrums in a descending order plus the FM spectrum 88-108 MHz.
In FIG. 3 is shown the downstream functions of the Control Station 1, to one of the feeder cables, which receives the multichannel output of the bridger amplifier 2 through directional couplers 6 and processes each TV channel separately, through the down converters 7 that provides a common I.F. band of frequencies 41 to 47 MHz. The outputs of these converters are connected with further directional couplers 6 to the input terminals of switching network 8. The output of the switching network connects the requested channel's I.F. to TV channel up-converter 9. This switching can be mechanical, electronic or any automatic type where a desired program can be sent to the proper channel converter through additional directional couplers 6 to feeder cable 10. Local TV program origination whether live or by tape is handled the same way. This is shown by videotape player 11 connected to modulator 12 for conversion of video to I.F. and is available to be switched to any subscriber. By this system the Control Station connects any desired I.F. modulation to any output channel on any feeder.
The FM signals are handled differently in that the broadband spectrum 88-108 MHz is maintained throughout; further directional couplers 6 connect the bridger amplifier's output to FM amplifier 13 and the various feeder coaxial cables 10. By this system the Control Station connects FM to all feeder cables.
In FIG. 4 is shown the downstream, upstream and control functions of the Control Station 1. The downstream functions are the same as shown in FIG. 3 with signals from bridger amplifier 2 being connected via directional coupler 6, being converted to I.F. by down-converter 7, being switched by 8 to the desired channel up-converter 9 and connected to the feeder cable 10 through a channel bandpass filter 14.
The upstream television signals from feeder cable 10 are fed through directional coupler 6, through the channel bandpass filter 14, through other directional couplers to an I.F. down-converter 7, then through the automatic switch network 8 to the desired channel up-converter 9 and through a directional coupler to the return trunk amplifier 3, in the Trunk and Bridger Amplifier and Control Station. These functions enable the TV or data return channels to be ultimately fed to the Cable System headend, there to be redistributed to any other subscriber.
The upstream control signals are fed to the frequency selective voltage control network 15 where they provide frequency selective voltages to control the automatic switching of both upstream and downstream signals. For a detailed description of this network see FIG. 5.
In FIG. 5 is shown various functions that are employed in controlling the switching network that allocates the television channels being sent and received by a subscriber. This is done by a network that receives and responds to a control signal from a subscriber. A subscriber can send this signal by modulating with a discrete frequency the lower R.F. band edge of the subscriber's allocated channel. All taps, cable, filters and accessories on the feeder cable 10 are two-way so this control signal is split off the feeder at the Control Station by a directional coupler 6, connected to channel R.F. bandpass filter 14, to an R.F. detector 16, then a low frequency bandpass filter 17 that accepts the desired frequency selective signal and feeds it to amplifiers and that develops a control voltage for the automatic switching. Items 16, 17 and 18 are components of the frequency selective control network 15 in FIG. 4. Items 6, directional couplers, which are in the control path after 14 are not shown on this FIG. 6.
The conversion of any incoming television channel at the Control Stations to an outgoing television channel is accomplished by converting all incoming channels to a common I.F. frequency, switching them by means of control signals and then reconverting them to the desired outgoing frequency.
The switching, which is not shown, can be typical of any of those that are employed in two-way cable television systems such as that shown at the program exchange in U.S. Pat. No. 3,801,705 of Gabriel, referred to above, for non-duplication or other services. It can be electronic, mechanical or any automatic type wherein the control signal from any subscriber will actuate the switching circuit and cause the desired program to be sent to the subscriber.
In FIG. 6 is shown a two-way subscriber drop which includes the two-way feeder cable 10, directional coupler 28 and an FM bandpass filter 19 to pass FM to the subscriber irrespective of TV channel allocation. The feedthru section of the FM filter connects all TV signals to a TV channel bandpass filter 14, to the subscriber's two-way interface terminal 20 and to the TV receiver 21.
The upstream TV transmitting circuit can comprise of a TV camera 22, microphone 23 and modulator 24. An upstream control signal transmitting circuit could include a lower band edge R.F. oscillator 25, a discrete low frequency oscillator 26 and a mixer or modulator 27. This control signal can be switched on by the subscriber's interface terminal 20.
While the principles of the invention have been described in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.
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