TWO-WAY COMMUNITY ANTENNA TELEVISION SYSTEM

• US 3,668,307 A
• Filed: 03/30/1970
• Issued: 06/06/1972
• Est. Priority Date: 03/30/1970
• Status: Expired due to Term

• Current Assignee: Harold W. Katz, Murray H. Miller, William W. Face
• Original Assignee: Harold W. Katz, Murray H. Miller, William W. Face
• Inventors: Miller, Murray H., Face, William W., Katz, Harold W.
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US05/024,009
• Time in Patent Office: 799 Days
• Field of Search: 325/3,5,54,308,309 178/DIG.13,5.6,5.8R,6 340/163 179/15AS
• US Class Current: 725/119
• CPC Class Codes: H04N 2007/17372 the upstream transmission being initiated or timed by a signal from upstream of the user terminal
• CPC Class Codes: H04N 7/147 Communication arrangements, e.g. identifying the communication as a video-communication, intermediate storage of the signals selecting H04Q
• CPC Class Codes: H04N 7/17363 at or near the user terminal

Abstract

A two-way community antenna or closed circuit television system or community cable television system which permits two-way communication (including voice communication) through a transmission center from and between various terminals, such as schools, homes, hospitals, doctor'"'"''"'"'s offices, community centers, industrial sites and the like. A control center including a properly programmed digital computer continuously interrogates the system over a forward control channel and receives responses from the terminals over a return control channel. The computer also controls transmissions between the transmission center and the terminals and between the terminals via the transmission center. Each terminal is provided with a control unit for communication with the control center. The system utilizes an appropriate bridging amplifier or other suitable means to convert to a two-way link a portion of the transmission cable interconnecting the transmission center and the terminals. The system also contemplates the use of channel allocations between 0 and 300 MHz, it being practical to allocate in this range certain portions for return transmission channels for programs originating at the terminals and certain portions for extra forward transmission channels for special programs originating at the transmission center.

Claims

1. A two-way closed circuit television system comprising a plurality of remote terminal stations connected to a central transmitting station by means of a transmission line capable of carrying simultaneously a plurality of communication channels including television channels, said system comprising:

a. means coupled to said transmission line for limiting some of said channelS, designated as forward channels, to signal transmission in the opposite or return direction, b. a control station connected via said transmission line to said central station and to said plurality of terminal stations for controlling access of said remote terminal stations to said communication channels and comprising a computer for continually and serially transmitting to said remote terminal stations via a forward control channel of said transmission line a list of digital code groups, each code group comprising an instruction word and a terminal address word, c. each terminal station comprising;

1. a digital control unit having a plurality of inputs and outputs and comprising;

a. address storage means for storing the unique address of that terminal station, 2. comparator means coupled to said address storage means for sequentially comparing each of said transmitted terminal address words with the stored unique address, 3. decoder means coupled to said comparator means and responsive to a match between said unique address and a terminal address word for decoding the instruction word in the code group containing the matched address word, and 4. control circuits responsive to the decoded instruction word for controlling access of said terminal station to said plurality of communication channels, d. a television receiver at each said terminal station and adapted to be electrically connected by operation of said digital control unit to selected communication channels of said transmission line, and e. said central transmitting station having means for transmitting on the forward television channels television programs on unique television channel carriers for reception by each television receiver whose terminal station has been granted access to a corresponding unique forward television channel by said control circuits.

2. A two-way closed circuit television system as defined in claim 1 wherein said system is a community antenna television system having a community television antenna connected to said central transmitting station, and said transmission line is a coaxial cable.

3. decoder means coupled to said comparator means and responsive to a match between said unique address and a terminal address word for decoding the instruction word in the code group containing the matched address word, and

4. A two-way closed circuit television system as defined in claim 3 wherein said request code is a request for access to a predetermined forward television channel, said computer containing program means for determining whether said terminal station is authorized access to said predetermined channel and, if authorization is determined, transmitting on said forward control channel an appropriate instruction word in the code group containing the terminal address word which matches the stored unique address of said terminal station, whereby said instruction word is decoded by said digital control unit to operate said control circuits to electrically connect the television receiver at said terminal station to said predetermined forward television channel for reception of the television program being transmitted thereon.

5. A two-way closed circuit television system as defined in claim 4 further comprising audio input means connected to one of said inputs of said digital control unit, and wherein said request code also contains a request for an audio return channel associated with said predetermined forward television channel, said control circuits being responsive to a decoded instruction word to electrically connect said audio input means to said associated audio return channel to permit two-way voice communication between the requesting terminal station and the authorized Other terminal stations, the voice communication on said associated audio return channel being modulated on an audio carrier unique thereto, and all authorized terminal stations having their respective audio input means convertible to said associated audio return channel so that voice communications from all said authorized terminal stations are modulated on said unique audio carrier, the voice communication on said predetermined forward television channel being modulated on the unique television carrier thereof, and means under the control of said computer for designating one of said terminal stations as a control terminal station, the digital control unit of said control terminal station controlling via said computer the access of the other terminal stations to said associated audio return channel.

6. A two-way closed circuit television system as defined in claim 5 further comprising means at said control terminal station for originating said television program, and means for transmitting said television program to said central transmitting station via a return television channel associated with said predetermined forward television channel, whereby said television program is transmitted over said predetermined forward television channel by said program transmitting means at said central transmitting station.

7. A two-way closed circuit television system as defined in claim 3 further comprising a television camera connected to one of said inputs of said digital control unit of a program-originating terminal station, and wherein said request code is a request for access to a pair of predetermined return and forward associated television communication channels for origination and transmission of a special television program to other terminal stations which are authorized by said computer to receive said special program, said computer transmitting over said forward control channel an appropriate instruction word in the code group containing the terminal address word matching the stored unique address of the requesting terminal station where the instruction word is decoded to connect said television camera through the digital control unit and said predetermined return communication channel via said central transmitting station to said predetermined forward communication channel to said authorized other terminal stations, said special television program being retransmitted by said television program transmitting means at said central station on said unique television channel carrier.

8. A two-way closed circuit television system as defined in claim 7 further comprising audio input means connected to one of the inputs of a second digital control unit, and wherein the request code from said second control unit contains a request for an audio communication channel associated with said associated pair of return and forward television channels, the control of said originating terminal station being responsive to a decoded instruction word to electrically connect said audio input means to said audio return and forward television channel of said transmission line to permit two-way voice communication between the second terminal station and the authorized other terminal stations, said voice communication being under control of the digital control unit of said program-originating terminal station so that only a terminal station authorized by said program-originating terminal station has access for voice input to said television program, said voice communication being modulated on said unique television carrier of forward television channel.

9. A two-way closed circuit television system as defined in claim 7 further comprising a second television camera connected to one of the inputs of a second digital control unit, and wherein the request code from said second control unit is a request for the transmission of a second special television program to said authorized terminal stations, the control unit of said program-originating terminal station being responsive to a decoded iNstruction word to electrically disconnect its television camera from, and connect said second television camera to, said pair of predetermined return and forward television channels, the access of a television camera to said channels being under control of the digital control unit of said program-originating terminal station so that only a terminal station authorized by said program-originating terminal station has access to said channels.

10. A two-way closed circuit television system as defined in claim 3 wherein the digital code groups are arranged in said list in order of increasing distance of the terminal stations from the central transmission station thereby permitting request codes to be returned from the individual terminal stations in the same order as the corresponding interrogation codes so that terminal address words do not have to be associated with the return request codes.

11. A two-way closed circuit television system as defined in claim 1 wherein the tuner of said television receiver is set at a predetermined channel frequency, and said digital control unit comprises means for selecting television programs on said transmission line under the control of said computer and for converting a selected television program carrier frequency to said predetermined channel frequency of said television receiver.

12. A two-way closed circuit television system as defined in claim 1 wherein said digital control unit further comprises an audio oscillator adapted to be modulated by the voice input to a microphone, and means in said digital control unit responsive to an instruction word from said computer to connect said microphone to said audio oscillator, thereby to permit voice signals to be transmitted on a return audio channel in said transmission line, said control station having means comprising filters for separating individual video and audio return channels and then combining corresponding video and audio channel signals and modulating them on said unique television channel carrier for transmission by said transmitting means as said television program on a corresponding forward television channel to other remote stations which are authorized by computer instruction words to receive said program.

13. A two-way closed circuit television system as defined in claim 12 wherein each digital control unit in said system comprises a plurality of audio oscillators preset to different frequencies, the corresponding oscillators in all of said digital control units being preset to the same frequency.