CA1203890A - Television information system - Google Patents

Abstract

TELEVISION INFORMATION SYSTEM

ABSTRACT
This television information system transmits selected video picture information to one of a number of subscribers who have television sets connected to the system. First, the subscriber makes a selection by transmitting a request to the head end. A central computer interprets the request, searches the available data banks for the information, and records it. Next, the information along with an identifying number is returned to the system and sent to a control station.
At the control station, the identifying number is used to route the information to a particular mode for associated with the subscriber who made the request. The information is stored and used to modulate a unique carrier frequency which has been dedicated to that subscriber.
The control station sends the modulated carrier frequency (containing the selected information) to a feeder line to which may be connected a number of subscribers, including the one who made the request. If the requesting subscriber's television set is tuned to his carrier frequency, he can receive the requested information. Privacy is assured by dedicating to each subscriber a different carrier frequency and associated television channel, and by filtering out all other channels which might be transmitted on the feeder line.
Standard, unmodified television sets may be used with this system;
and rapid retrieval of information from large data banks is possible.

Description

lZ03890 TELEVISION INFORMATION SYSTEM

BACKGROUND OF THE INVENTION
Cable Television A significant proportion of television entertainment is presently delivered by way of cable television systems. In general, these systems can receive broadcast television signa]s on a common antenna or set of antennas, amplify the signa]s, and distribute them along tr~ncrnicqion lines either at their original frequencies or after conversion to different frequencieq. The tr~nqmi~ion lines are connected to the television sets of the system's subscribers, usually through a deco~inE or filtering device which is intended to prevent non-subscribers from receiving the signals.
Prequency conversion is often necessary in systems which handle programs broadcast from outside the local area, since there is a good chance that signa]s will be received from two different stations which operate on the same l~h~nnpl (A standard broadcast television channel in the United States is a band of fre~ nr~i~ 6 MHz in width.) Cable television systems are also well suited to transmit non-broadcast programming to their subscribers. Such programs originate within the cable television system itself, for e~mple by displaying a motion picture to a television camera and using the resulting electrical signal to mcri~ te a carrier freqency.
In either case, cable television systems consist of four main parts:
a head end, the main trunk cable distribution system, feeder cables and drops from feeder csble6 to the subscriber's TV set. A cable television head end includes the television receiving antennas for ofi-air pick up and microwave and/or satellite receivers for other direct television 120~8~0 programming as well as equipment that originates local programming.
From the head end, trunk lines transport the signal to feeder lines which carry signals past each home.
The integrity of trunk cables is not meant to be breached by tapping off signals for direct distribution to subscriber homes. Rather this ic accomplished with a feeder cabIe. The signals on feeder cables come from amplifiers (bridger amplifiers) bridged across the trunk cable at distribution points. Therefore, in many cases, feeder cables must parallel or backtrack side-by-side with the trunk cable in order to have a cable that can be tapped to feed a signal to subscribers. Signal losses in feeder cables may require line extender amplifiers approximately every 1500 feet. These multi-channel amplifiers c~use problems themselves. Repeated amplification of broadband television signals causes noise, inter-n~od~lAtion distortion and echoes, illC. ea~ing with each amplificstion, thereby limiting the distance that signals can be transmitted while maintaining a given standard of picture quality.
Cable losses increase with frequency as well as with distance.
Thus, the superband VHP portion of the cable s~e_tr~r", 216 to 300 MHz, is subject to greater loss than the highhQnd and lowband VHP, 54 MHz to 216 MHz.
While the TV channel allocation spans the spectrum from 54 to 890 MHz a cable television system utilizes only a small part of this spectrum. The first cable television systems were built in the early 1950's to provide broadcast l hQnnelC to subscribers in areas that could not receive off-air signals. These early 5 chhnnel systems used the standard television fre~l~Pnci~pc from 54 to 88 MHz for distribution of these broadcast rh0nnph. When the state of the art sdvanced to include 12 ~h~ nl~lc~ cable used the high VHF spectrum of 174 to 216 MHz as well. These 12 rhRnnelc could be received without a converter. To se to 21 rhRnn~plc~ cable systems used the midband spectrum from 108 to 174 MHz to add nine Ctl~itionRl th~nnPlc; these rhR~nelc required using a frequency converter since the television set tuners could not accommodate these midband chRnn~lc. Current 35 r -- ?~ systems add 14 ad~ rhRnnplc by using 216 to 300 MHz. To accomplish this, ~re~ euc~ converters were upgraded. Plans e~ast now to add another i2(~38 25 channels, extend the cable television spectrum to 450 MHz. ThusJ
as cable television systems add ch~nneh~ they use i,.c ~ gly higher frequen~ iec~. This can only be done at the cost of greater signal attenuation.
The upper frequency limit on trunks is established by the performance of linear broadband amplifiers and by trunk cable attenuation, which i,.c. e~3es with i..c~ ing frequency. Feeder cable length is limited to about 1500 feet by the attenuation at the highest fre-J,~ ;~ carried on the feeder. Therefore, the gap between the highest VHF television frequency at 216 MHz and the lowest UHF
television frequency at 470 MHz establishes a natural barrier to attempted csrriage of both VHF and UHF signals on a cable system.
Bidirectional Unicable Switching System An improvement in cable television system technology was introduced by U.S. Patent 4,077,006, issued to Nicholson on February 28, 1978. Briefly, the Nicholson patent describes a bidirectional cable television system in which each subscriber has a dedicated television carrier fre~luenc~r and channel for receipt of any signals which the system is capable of sending to that subscriber, except for FM radio broadcasts which are sent to e.e.~ e at the original frequenci~ (in the band from 88 to 108 MHz). The heart of Nicholson's system is the control station at the head of each feeder line (at its intersection with the trunk line).
The control stations receive all incoming television programs transmitted along the trunk line, as well as requests from subscribers who wish to view a particular, ~ The jnCOmil~ ,'~ ~lc are first converted to a single intermediate l eq~.en.~ r - ~1, then the particular program that a subscriber wishes to view is routed by switches to a freq~enc ~
oonverter which ~ rts it to the subscriber's dedicated ch~nn~l The selected program is finally output to the feeder line together with programs requested by other subscribers and converted to their dedicated At the subscriber terminal, one ~--1~cs filter separates FM
radio t~r~dcucts from the feeder line, and another separates the programming which was converted to that subscriber's de~ ted r - ?l For further details regarding this system, the reader is referred to the Nicholson patent itself.

120~8~0 Videotext Systems In the past few years, the revolution in information technology has led to the research, development and field testing of "videotext"
systems --a technology which uses electronic devices for the widespread dissemination and retrieval of information. These systems have in common the ability to allow subscribers access to large data bases of information using a modified or adapted television terminal.
While there is little doubt that these "electronic newspapers" have widespread applicability, use on a mass basis has been delayed by the high costs of developing these new technologies and by the perceived obstacles to acceptance by consumers and information providers (cost of terminal equipment, cost of system usage, primitive display systems).
While existing system delineations are blurred, the following summary categorizes them as either "viewdata" or "teletext."
Teletext systems are one-way videotext systems in which information in digital form is placed on unused portions of the television signal by means of special terminal equipment built-in or attached to a television set. Unlike viewdata, where the subscriber interacts individually with the data base, in teletext the complete data base is cycled continuously and it is available simultaneously to all subscribers.
Using a keypad, the desired information is selected by the subscriber as it iS cycled, stored in a local memory, decoded and formatted for use by a character generator, and displayed on a television receiver.
In the United States the makeup of a television picture limits, for all practical pu. ~06es, information tr~nQ-miQ-Q;on of teletext to only two lines (17 and 18) of the Vertical B1P ~ lE Interval (VBI). Therefore, the potentisl size of the teletext data bsse is limited by the amount of information that can be cycled in a time period acceptable to the subscriber. Using these two lines, 90 pages of text can be cycled in 60 seconds; field tria]s have indicsted thst this is an unacceptsble limit.
Experiments using VBI lines below 17 snd 18 to i.~c~ease the information capscity have not been very s~lec~- l ul.
Teletext has many obQ-t~ l~ to widespread use and consumer scceptsnce. Some of the most obvious ~re the retrieval time and size of the dsta bank, the cost of e~nirment in the home, the rudimentary 120~8~

graphics, and the absence of privacy. Because the s~s~ . iber selects information as it is cycled, the size of the data bank is limited by an acceptable waiting time. In the U.S. where only 2 lines of the VBI
are available for data transmission, teletext is, for all practical purposes, still a narrowband and consequently slow system. To use the teletext system, the subscriber must rent or p~ ch~se a modified television receiver with a keypad, a decoder with s r~" a character generator for visual display, and a pQge grabber. A less-sophisticated version has a keypad, set top mod~ qtQr and decoder. Even the most primitive terminals presently cost several hundred dollars more than conventional television. Even with mass proJu~ lion, the terminal costs will be too great for the occ~ l uær. The primitive ~lrh~ lmeric and graphic displays have limited marketability. 13ec~u~ all subscribers have sccess to the same information at the same time, teletext has limited acceptability for information providers who want to restrict their information to special users. Teletext a]so has limited appeal to information providers because the one-way system makes it impossible to record and charge for the specific page requested.
Viewdata is a nar.o. ~nd, interactive switched system employing t~lPphon~ lines to transport information from data banks to sùbscribers.
In a viewdata system, typically the subscriber requ~l~ information via a keypad or a keyboard attached to a tel~ph~me line. This information, stored either in central or l~ e d data banks, is forwarded to the subscriber in page packets, stored in the interactive "terminal" and formatted for display on a color television rece;._r. The display consists of ~ meric characters and stylized graphics.
Access to viewdata systems involves indivi~ ed) interactive tree ~ -rcbes. An information request leads the subscriber to general information; the subscriber refines his request, which leads to more specific p~ges. Thùs, the process often involves several interactions before the subscriber obtains the desired infotmation.
Infol ~tion providers therefore face 8 mapr c~ ~ge: to design the "search" system to ensure that the subscriber does not get lost or frustrated in his data search. The information provider, in ~lr~ct~l~;ng his information, must think like his subscriber and must strive to create 1~03890 a "friendly system" which will allow the subscriber to retrieve the desired information with as little trouble as possible.
To accomplish this interaction, typical viewdata terminal equipment consists of _ keyboard, microproce:isor, memory, display controller, a color television and a 1200 bit/s modem to allow trAn~mi~sion of digital data over standard telephone lines. A separate dedicated telephone drop is needed to Hvoid tying up regular telephone service. The narrow telephone bandwidth limitation of the viewdata system frequently results in lengthy retrieval intervals~ ~or example, in a typical viewdata system, a simple tree search, involving perhaps five interactions, can often take 60 seconds because of the wait time necessary for each page to be displayed on the television screen (6 to 11 seconds per page). A more complex search can take evsn longer.
In addition, while the system allows the subscriber access to a very large central data b~se, or an unlimited number of locAli7ed or specialized data bases, the system can easily be overloaded when subjected to very many simlllt~neouc requests.
Because each information request is individunli~ed -- only the subscriber receives the information requested over his own private telephone line -- the system can be adap~ed for groups requiring a secure chAnnf n Typically, the graphic display systems for viewdata are rudimentary; they are not capable of producing true photographic representations. Instead, alphAnl~merics and picture-like graphics are produced by using _ mosaic sub-element matrix of two columns and three rows per character. The process is primitive _nd slow. A second generation viewdata system, now under development, has refined graphic capability. Its graphic display of 960 lines by 1280 picture elements, 1,228,800 pixel locflffon~, provides nearly 20,000 times as much detail as the earlier systems. mis refinement is not without its tradeoffs: the system's A~ b_~,.--etric decoder costs ne_rly ten times that of a first generation ~coder, further, transmitting a graphic image using this "best cAse" stylized graphic system may take hours.
While ~ ;h~ much potential, the widespread adoption of viewdata systems faces several types of obstacles, int l~ inE length of 1'~03890 retrieval time and complexity of the search process, cost of equipment in the home, cost of using the system, and rudimentary graphics.
The u e of narrowband telephone equipment means that a simple request may take ac long as 60 seconds; more complex requests may involve much longer times. Because of the interactive nature of the system, a subscriber may become frustrated in his search if the information is not sufficiently coded and cross referenced. The subscriber may not find what he needs.
In order to use a viewdata system, the subscriber, in addition to a dedicated telephone line, needs an adapted television receiver equipped with a keypad, memory, microprocessor, and display controller. Prototype models cost approximately $2,000-$3,000. Even if mass production could substantially reduce the price to a target of 50% more than a standard color television, only the most serious subscribers (t~cine~c~s and professionals) could afford the system.
A typical system involves three charges: a local telephone call, an overail charge for the use of the system on a per minute basis (with variations for peak or off-peak usage), and a price for ucc~i,i,-g the data base. This last charge is a pe~ page price est~bliched by the information provider. Rates vary according to the type of information requested, ranging from $.02 to a maximum of $1.00 per page.
Advertisements may be free, an index to information available at nominal rates, and specialized, technical information comm~n~ the highest rates. Thus, a typical request may cost $.25 a page, far above the cost of a daily nei._~per or even a phone call to elicit the equivalent information.
While the display can present textual information adequately, the inability to reprvduce photographs makes these systems po~r candidates for mass m& k~til.z where the ability to see the actual product and compare it with similar products is essential.
Cable Tele~, i;.;on Systems With Videotext Cable television systems, ~ltl~ough used only experimentally for information retrieval and ~lisce nin~tion~ have many inherent advantages.
The greater s~;lr.~lll available to cable systems allows them to transmit many -h~ le?~ -- older systems normally carry 12 c=h~n~ q and newer ,J

1'~0~890 ones 35 rh~nneh (although systems capable of as many as 128 channels are currently being proposed in larger urban markets). Thus, the allocation of Q large amount of spectrum space to data is possible.
Further, because the channels are wideband, data can be transferred faster.
Fin&lly, the wide bandwidth available through cable television systems provides for tr~n~mi~s;on of standard television photo images in 1/30 of a second (in addition to ~ll.hA~ e.;c and graphic representations).
However, in order for a subscriber to "hold pictures" each terminal device would have to be e~ ~ed with a "frame grabber" which would select the television photo image frames, store them in a local memory at the terminal location, and refresh them for the television screen.
"Frame grabbers" currently have only been produced in small quantities and are very eA~ens.~_.
Since all cable systems provide a one-way distribution to the home, teletext, which is a one-way system, can easily be adapted for cable systems without limiting use to lines in the vertical bl~nking interval. An entire television channel could be devoted to teletext.
However, in order to store photo images, a frame grabber would be required at the subscriber location, in acl~lition to the terminal equipment n~cec~ry for broadcast teletext (keypad, decoder, ~ Sor).
Viewdata (interactive) applications are a]so possible with cable telc~i;,;on systems. Two-way systems already allow for return data from subscriber locations. Older one-way systems will require the addition of amplifiers and filters, or relrofill E~ with Q second cable.
Cable ~ I..o.l~, linked via satellite, can provide a viewdata user with access to data banks at different locations, or with a central data bank located at the head end.
Cable television, which has already est~hli~hed the tradition of monthly subscriber charges for services, can market videotext as an add-on service, offering subscribers t~leteYt, viewdata, or both, for a monthly service charge, or e~ ~ E;Ug per page on computer interfaced two-way systems.
While the use of cable television solves some of the problems inherent in teletext or viewdata by providing greater st~ectr.~l-- and 1~Z03~V
g bandwidth, and is capable of transmitting photo images, there are still obstacles to mass use, including the cost of terminal equipment, but problem of privacy, and the design of existing systems.
Any market resistance to high subscriber terminal costs which would limit marketing of viewdata or teletext would also limit cable television. The advantage of cable television over viewdata (not counting the elimination of exorbitant telephone line costs) is the ability to display "photographic" images which could be transmitted at a rate of 30 per second. However, this advantage is immediately weaken-ed or even dissipated by the prohibitive cost of installing a "frame grabber" with memory storage at each subscriber loca-tion. Mass marketing is inhibited or vitiated.
SUMMARY OF THE lNv~NllON
An object of an aspect of the present invention is to adapt the latest cable television technology, as exemplified by the Nicholson patent, to the dissemination and retrieval of information. Using the present invention, individual sub-scribers are able to receive selected information from databanks through the same system which brings them television programming, and to receive it on their own, unmodified tele-vision sets. Accordingly, an object of an aspect of the present invention is to provide information to subscribers without the need for expensive term- n~l equipment at the sub-scribers' locations.
An object of an aspect of the present invention is to give subscribers quick access to information from a large data bank, a combination which is impossible under existing teletext systems. An object of an aspect of the present invention is to maintain privacy in an information retrieval system by giving each subscriber a dedicated television ch~nnel;
a collateral object is to maintain privacy in such a system without the need for each subscriber to have an information-dedicated telephone line.

1~038~0 - 9a -An object of an aspect of the present invention is to allow subscribers to an information-delivery system to receive photographic information and not merely stylized graphics.
A cable television and information system in accordance with an aspect of the present invention is capable of transmitting selected data to subscribers. In addition to the VHF television channels on which each sllhS~r;h~r i,~

1'~03~0 receives regular programming, a UHF television channel is dedicated or assigned to each subscriber to deLiver information. The use of an entire 6 MHz UHF channel for information guarantees that a great deal of information can be transmitted in a short time, thus satisfying the requirement for minim~l retrieval time. The large bandwidth also aLlows photographic information to be delivered to subscribers' television sets.
This cable television system inrh~d~ a head end, trunk lines, bridger ~mplifiers~ control stations, feeder lines and a central computer connected to the head end. The control stations include an information retrieval system for e~.lr~c~ information from the trunk lines and COI~reA ling the freq~)en~ ie~ ar. ~i lg the information to the proper dedicated UHF
frequencies. The cable television and information system also includes a subscriber station which in~lude~c a keyboard for selection of data to be displayed.
In the above csble television and information system, speci~ ed e~-ipment is concentrated at the control station, out of reach of the subscriber. Thus, the amount of speci~li7.ed e~lui~ e t required is only a fraction of what would be needed if each subscriber's home were so e.l.-ipped, since one set of e~uirment in this system can serve many subscribers.
The subscriber generates data selection instructions identifying the desired data by typing the "plopr;ate characters on the keyboard. Radio lre~uen~ ~ signals co~e~ to the k~trokef and to the station's identification number are transmitted along the feeder line to the control station, which ~ o~e~ and stores the signals. They also travel to the head end. At the head end, these data selection i,c~tr~ ons are routed to the oentral computer, where they are A~ codeA,-The central & Euter locates the selected data, either in its owninternal data sources or in an external data source, if one is available to the system. The central computer then retrieves the data from the source, Aecodes it to a "scene" if it is teletext, formats it for display on ~ telc.- set, and, if r-~`ff ry~ all_~hes an id~...lit~ number to the data. This number will be used by the control station to determine whether to extract the data from the trunk, which subscriber requested the information, and, therefore, at which dedicated UHF

iZ038~0 "

frequency to transmit it along the feeder cable. Finally, the central computer sends the selected data to the head end, where it is transmitted along the trunk line to the control station.
At the head end, data may be stored either in digitHl form, or, especially in the case of still slides, in analog form. The system has the option of transmitting the selected material along the trunk line to the control station in either digital or analog form. Digital transmissions can be made distortion-free, while analog trRncmiC~iQn may be subject to some distortion. Digital tr~qnqmic~;on is slower (by about a factor of 10). A single television frame in digital form would require a trcncmi~sion time of about 1/3 second whereas frames in analog form can be transmitted at a rate of 30 per second. In the preferred embodiment, however, all information is transmitted from the head end to the control station in analog form; conseguently, if it is stored as digital data, it must be converted to analog by a digital-to-analog (D/A) coRverter. The head end uses the analog information to modulate a band of freql~arcie-c designated for do..~ eam communication -- the dG..I~lream channel-- which is preferably within the VHF range.
At each control station, the identifying numbers co..~.7t,onding to the data requests of subscribers connected to that particular control station are stored. The data selected by individual subscribers then is extracted from the kunk line by a frame grabber. Each subscriber's data or information, in the form of a television frame, is routed, in accordance with the identifying number, to one of several frame stores at the control station. The data frame is stored so that it can be cor.ti,..~llsly trsnsmitted to the subscriber. The information is stored in digital form, converted to analog by a digital-to-analog (D/A) converter, and then used to moA~lcte a unique carrier frequency t,o~ g to the particular subscriber's television set.
The modulated carrier frequency occupies a standard UHF
television channel dedicated or scciG~ed to a particular subscriber. All subscribers are ~ric~ed different UHF television ch~nn~lc for trcn~mic~ion of information. At the output of the control station, the carrier qted with the selected data is inserted into the feeder line which serves the home of the subscriber who requested the data. VHF

1'~03890 programming and information transmission on dedicated UHF channels occur on the same feeder lines. At the subscriber's terminal, a filter is connected to the subscriber's television set to block all channels except the ~h~nn~lc bringing him programming or information. Only VHF programming channels and the dedicated or assigned UHF information channel reach the subscriber's set.
With this invention, the individually assigned subscriber channel can be received on a standard television set. Subscriber terminal costs are limited to a simple keypad and oscillator, since the bulk of the equipment neCeSSRry for information transmission is located at the common control station. When using a common feeder cable for both television programming and videotext, entry into the house can be made by using a single drop with a splitter at the rear of the television set.
An important advantage of this system in information retrieval is the assurance of privacy. Because each user has his own private dedicated h~nnPl, only the individual requesting information will be able to receive it. Unlike conventional cable television where the cable functions as a "party line," here each subscriber has his own private line.
This invention can use either the regular cable television feeder line or a separate feeder line. With a separate feeder line, the number of feeder lines from a single control station can be ine. ~ased and the number of dedicated ch~nnelc on each line can be increased by using the spectrum from 890 MHz down to 50 MHz for a total of 140 channels per feeder.
Another feature of this invention is the use of the concept of ~n inverted spectrum. As pr~viou~ly noted, cable television was forced to use i--c.e~ ~ly high frequenciPc ~s Rd~liti-~n~l programming services created a demand for more ch~nnph. This use of higher frequencies caused the associated problem of i... reased attenuation. The greater the distance these high frequency signaLc were transported, the greater the si~nal 106s. To avoid this problem, the present invention ~ssigns a 6 MHz channel to each subscriber on an inverted basis. Channel al~ tionc consist of the UHF ~h~n-Plc 14 through 83, using the spectrum 470 to 890 MHz. There are 70 ~h~nnPIc available in this range so that 1~0~90 on a single feeder cable, 70 different subscribers can each be allocated a channel. Using the inverted spectrum concept, the subscriber closest to the control station is assigned the highèst channel - 83 (884 to 890 MHz) - and the most distant subscriber the lowest - 14 (470 to 476 MHz). This allows the highest frequency ~subject to the greatest attenu-ation with distance) to be transported the shortest distance.
Therefore, each subscriber receives a clear picture without the need for amplifiers along the feeder cable.
If subscriber density exceeds 70 homes per mile, then non-standard channel assignments are made in each cable television system on the unused portion of the spectrum until it overlaps the basic system, which will be at about 216 to 300 MHz in current cable systems. Also, as the UHF frequency falls below 470 MHz, a one-channel set-top converter will be required. Using this distribution pattern, the present invention can accommodate a virtually limitless number of program services since only the program selected by the sub-scriber need be transported along the feeder to the sub-scriberls private line.
.

i~(l3~90 - 13a -A cable television information system for transmitting video picture information to television receivers at subscriber terminals on a cable distribution system, said cable distribution system including a head end, at least one trunk line connected to said head end, at least one 5 bridger amplifier connected to said trunk line and at least one feeder cable connected between said bridger amplifier and said subscriber terminals, said cable television information system comprising:
information storage me~ns for storing video picture information;
information rétrieval means coupled to said head end and said 10 information storage means for retrieving video picture information from said information storage means and supplying the video picture information to said head end for transmission on said trunk lines of said cable distribution system;
control means associated with at least one of said bridger 15 amplifiers and at least one of said feeder lines for capturing and storing the video picture information on sQid trunk line, said control means including transmission means for transmitting the video picture information to one of said subscriber terminals on a television channel dedicated to said one subscriber terminal.

2 0 A cable television information system for transmitting information to television receivers at subscriber terminals on a cable distribution system including a head end, trunk lines connected to said head end, bridger amplifiers connected to said trunk lines and feeder cables connected between said bridger amplifiers and said subscriber .~

i;~O38~

- 13b -terminals, said cable television information system comprising:
information storage means for storing information;
ulformation retrieval means coupled to said head end and said information storage means for retrieving specified information from said information storage means upon request by one of said subscriber terminals, said one subscriber terminal including request means for requesting the specified information and transmitting a request to said information retrieval means over said cable distribution system, said information retrieval means supplying the specified information to said head end for transmission on said trunk lines of said cable distribution system;
control means coupled to said trunk lines at a location corresponding to the location of the bridger amplifier and feeder cable associated with said one subscriber terminal for capturing the specified information, said control means in~lu~linE storage means for storing the specified information and tr~ncmiecion means connected to said storage means for repetitively transmitting the specified information stored in said storage m~ans to said one subscriber terminal on a television channel dedicated to said one subscriber terminal.
In a cable distribution system inl~lutlinE a head end, trunk lines connected to said head end, bridger amplifiers connected to said trunk lines, feeder cables connected to said btidger amplifiers and subscriber terminals connected to said feeder cables, a cable television information system for transmitting video picture information to television receivers at said subscriber terminals, said cable television inform.aticn system comprislng:
information storage means for storing video picture information;
information retrieval means coupled to said head end and said - information storage means for retrieving video picture information from said information storage means upon request by one of said subscriber termina]s and supplying the video picture information to said head end for tr~nQmi~ ;on on said trunk lines of said cable distribution system;
control means coupled to said trunk lines at 8 location C~ to the location of the bridger amplifier connected to the

3 5 feeder line ~nnected to said one subscriber terminal for capturing the `,` -1'~038~0 -- 13c --video picture information, said control means including storage means for storing the video picture informstion and trA~cmicsion means coupled to said storage means for repetitively trancmitting the video picture information stored in said storage means to said one subscriber terminal 5 on 8 television channel dedicated to said one subscriber terminal.
In a cable television system containing 8 plurality of television receivers connected to a tr~ncnliecion line for transmitting television signals in~luAi~ programming to the receivers, wherein selected data is transmitted on the tr~r~cmiccion line along with the programming, 10 an information system for displaying the selected data on a selected one of the television receivers, comprising:
data extraction means connected to the transmission line for extracting the selected data therefrom;
switching means connected to said data extraction means for 15 routing the selected data in accordance with the identity of the selected one of the television receive.R on which the data is to be displayed;
storage means connected to said switching means for storing the selected data; and a plurality of r~od~ tQrs, each of said modlll~tors being connected 20 between said storage means and the~ tr~cmicciQn line and operating at a unique carrier frequency ~csoci~ted with a particular television receiver, to ~cd~ te the carrier frequencies with the data stored in said storage means.
A method for transmitting video picture information to a 25 ~elected one of a plurality of television receivers on a cable distribution system which i-^lu~ec a feeder line ~rnected to the television rec~:~,e,~
and a frame store, said method comprising the steps of:
storing the information in the frame store;
modulating a carrier f~e. ~ , with the stored information, said 30 carrier fr.;qu_n~ being ~soci~ted with the selected television receiver;
Ir~ r -~itting the rnoi~loted carrier frequency along the feeder line; and tuning the selected telo~iiaion receiver to the carrier frequency.
A method for transmitting video picture information to a 35 r~ ling subscriber's terminal on a cable distribution system which "~

i~ 0~90 - 13d -inrl~ld~c a head end, a trunk line connected to the head end, a plurality of frame stores coMected to the trunk line, a feeder line connected to the plurality of frame stores, and a plurality of subscriber terminals connected to the feeder line, said method comprising the steps of:
generating a request for the information at the requesting subscriber's terminal;
receiving the request at the head end;
acquiring the information at the head end;
adding a unique identifying number, associated with the requesting subscriber's terminal, to the information;
transmitting the information on the trunk line;
storing the information in the frame store;
mod~ tinE a carrier frequency, associated with the identifying number, with the information;
transmitting the mod~ ted carrier frequency on the feeder line;
tuning the reguesting subscriber's terminal to the carrier frequency;
and tuning all other subscriber terminals to frequencies other than the carrier frequency.
2 0 A television information system for transmitting video picture information to television receivers at subscriber terminals on a distribution system, said distribution system in~ AinE Q head end and at least one feeder line connected between said head end and said subscriber terminals, said television information system comprising:
information storage means for storing video picture information;
information retrieval means coupled to said information storage means for retrieving video picture information from said information storage means;
control means connected to said information retrieval means ar.d said feeder line for capturing and storing the video picture information retrieved by said information retrieval means, said control means inf-ln~linE
tr~ncmlcsion means for transmitting the video picture information along said feeder line to one of said subscriber terminals on a television channel dedieated to said one subscriber terminal.
A television information system for transmitting information `F~

1'~03890 - 13e-to television receivers at subscriber terminals on a distribution system including a head end and feeder lines connected between said head end and said subscriber terminals, said television information system comprising:
information storage means for storing information;
information retrieval means coupled to said head end and said information storage means for retrieving specified information from said information storage means upon request by one of said subscriber terminals, said one subscriber terminal ;~cR~-l;ne request means for requesting the specified information and transmitting a request to said information retrieval mesns over said distribution system; and control means coupled to said information retrieval means and said feeder line ~sociated with said one subscriber terminal for capturing the specified information from said information retrieval means, said control means including storage means for storing the specified information and trunQmi~s;on means connected to said storage means for repetitively transmitting the specified informstion stored in said storage means along said feeder line to said one subscriber terminal on a television channel dedicated to said one subscriber terminal.
Other objects and features of the present invention will be spparent from the following description taken in Col ne_lion with tt~e accompanying drawings.
BRIEF DESCRIPI ION OF THE DRAWINGS
Fig. 1 shows the electromagneffc spectrum from 0 to 300 MHz, giving the An~atione of several bsnds snd nomencl~tnre of several chAnn~lc.
Fig. 2 is a block diagram of a prior srt csble tclo.-~ion system.
Fig. 3 is a block diagram of the subscriber terminsl of a prior art videotext information system described above as teletext.
Fig. 4 is a block disgram of the subscriber terminal of a prior srt videotext informstion system described above as viewdsts.
Fig. S is a block diagrsm of the subscriber terminal of the present - invention.
Fig. 6 is a block diagrsm of an entire informstion system in ec~rd--~e with the present invention.
Fig. 7 is a detailed block diagram of the control station which is a part of the present invention.
A

l'hO~890 Fig. 8 illustrates one embodiment of a feeder cable system in accordance with the present invention.
Fig. 9 shows detaiLc of subscriber drops in the system of the present invention.
Fig.c. 10 and 11 are diagrams of the electromagnetic spectrum from 0 to 890 MHz, showing ~h~qnnçl~ svailable for use with the present invention.
Fig. 12 is a flow diagram for the computer program of the central computer used with this invention.
Fig. 13 is a flow diagram for the computer program of the mini-computer used in the control station of this invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 shows the allocation of VHF broadcast television channels and other radio ch~nnelc. A conventional cable television system delivering standard VHF channels and PM radio will transmit the band of frequencies from 54 to 108 MHz and the band 174 to 216 MHz to all subscribers. Subscribers can therefore receive VHF television and FM radio on unmodified receivers. A cable television system using a dedicated channel for each subscriber, such ~s described in the Nicholson patent, U.S. Patent No. 4,077,006, as well as a system which transmits a greater number of programs than can be shown on the twelve standard VHF ch~nn~lc~ will make use not only of these standard rhPnnel~ (2 through 13) but also of the midband and superband ~h~nnelc (A through W). Conce~J~ tly~ a cable system which does not give each subscriber a dedicated channel can televise 35 programs to an unlimited number of subscribers. On the other hand, the system described in the NichoLcon patent can televise an unlimited number of programs to 35 subscribers on each feeder line.
Fig. a illustrates a typical cable television system. At the head end 100, e~J. ;I. ent is provided to receive incoming television programming by various means or to create locally-originated programs. After smplification snd any other nececssry signal procs~ , all ch~nnelc are transmitted at their original fre~ nciP~ from 54 to 300 MHz, along ~e trunk line 102. Although only one trunk line is shown, there may be seversl, depending upon the particular system's design. Trunk lines ., 12(~3~390 102 coMect the head end 100 with all bridger amplifiers 104.
The bridger amplifier 104 is a conventional unit (for example, Station SP-2T-2W using two TF-30 high-low split filters, munufactured by Jerrold Electronics Corp. of phil~delrhia, Pa.). It amplifies both upstream and downstream signals. The upstream signals, if any, will most often be requests by subscribers to view p~rticular programming, although some systems may enable subscribers to send other signals to the head end.
The subscriber's television set 110 is attached to feeder line 106 through any nec~sry filters and converters 107. The set 110 is a standard television receiver able to receive VHF channels 2 through 13 and UHF channe]s 14 through 83. If programming is to be transmitted along feeder line 106 on other than these standard channels, a converter will be nec~ry.
A subscriber terminal for a videotext information system called teletext is illustrated in Figure 3. Data, as well as normal television programming, is received at the subscriber's antenna 112. Although an individual antenna can be provided for each subscriber, community antennas are equally useful with teletext. Television programming is delivered directly to the antenna terminals of ~e unr-o~lified television set 110. lncominE signals are also sent to the decoder and character generator 114.
8ecause all available data is cycled continuously in a teletext system, in order to view a particular psge of data on a television set, the subscriber need only key his request into his keypad 116. This request is proce~s~ d by the decoder and character generator 114, which selects the requested page from the continuously-transmitted dsta, decodes it into charscters for television display, and sends the characters to the on ch&r.nel ~nod~ tor 118. There, the data is used to modulate the csrrier frequency for the television channel on which the subscriber recei~es data. The data-modlllated carrier is then input to the ~n o~lified television set 110, where it is demodl~lRted and the dats viewed by the subscriber.
Pigure 4 shows the subscri~er terminal of another type of videotext system called viewdata. Subscribers to viewdata receive informstion ~'~03890 through a dedicated telephone 120, which provides two-w~y communications with the data source. Reguests for information are typed into a keyboard 122, encoded by the decoder and charscter generator la4, and modulated for tel~hone tr-A~ncmiQcion by modem 126.
Requests are then transmitted slong telephone lines to the data source, where the requected information is retrieved and transmitted back to the subscriber. Modem 126 ~ -1Ate~ the incoming data, and decoder and character generator 124 decodes it into characters which are then d~e,l~ed on the subscriber's television set 128. The viewdata television set 128 is a - ~c~ set, influr~ E the decoder and character generAtor 124 and the modem 126.
The subscriber terminal of the present invention is shown in block diagram form in Fig. 5 _nd is generally identified by reference number 129. Coaxial cable 130 is a feeder line in a cable telc. idon system which carries television programming to the subscriber's unmodified television set 110. A pn-lpAcs filter 132 is interposed between cable 130 and television set 110 to block all ~req~ ~nci~C except the subscriber's dedicated UHF info. offon chAnn~l- For television program reception, a parallel VHF bt - dpAcs filter 108 would be in~ lude~l The subscriber wishing to view information first typec an "all clear" signal into the keypad unit 134. Keypad unit 134 contAinc a small memory and an qscill~or in a~ liti~ to the keypad. If the keypad is, for eYomE~Ie, the standard twelve-button r ~ ;cal type, the all clear signal may be a single k~.J~lroI-~ on one of the two non nu-..erical L~tt This signal clears the keypad's memory and prepares it to receive a new data request. Next, the subscriber keys in the cstalogue number indi~ti.~, which data is to be displayed on his tclc.i~ion. (He may obtain this number, for eY~ , from a printed catalogue distributed by the cable system operatot; or the catalogue itself may be availsble ele Ironi~lly, by way of the infol ~ti--- system of the present invention.~
As the catalogue number is entered, it is stored in the memory. When the entire number has been stored, the subscriber types in a "transmit"
dgnal (which, once sgain, mQy be one of the two non-numerical buttonc on a t el~ tl~n k~r1) causing the data request, which is made up of the catQlogue number, plus a station identification number which has -iZ(~389~) been preset within the keypad, to be transmitted as a radio-frequency pulse train to the control station. Transmission of the pulse train is accomplished at the radio frequency of the keypad's oscillator, which operates on a return channel (a band of frequencies designated for upstream trQnemi~sion) preferably within the range from 6 to 30 MHz.
Many keypad oscillators may operate on the same return channel. A
low-pass filter 136 at the output of keypad unit 134 ensures that only signa]s below 30 MHz are passed to the cable 130, thus preventing interference with television programming and data being transmitted along the cable.
Figure 6 shows the cable television system of Fig. 2 modified in accordance with the present invention to deliver selected data to subscribers over dedicated UHF television ch~nnel~. A subscriber selects data to be viewed on his television set by generating data selection instructions as described above in connection with Fig. 5. The instructions are transmitted from subscriber terminal 129 along the feeder line 106 back to the bridger amplifier 104 and control station 140. The control station, whose operation will be described in greater detail below, (3emod~ t~s the data request and stores both the station identification number and the catalogue number of the data. At the same time, the data request also passes through the bridger amplifier 104 which amplifies it and switches it onto trunk line 102 which carries it to the head end 100.
At the head end, central computer 138 demodulates and stores the data selection instructions. Computer 138 locates the selected data using its catalogue number by searching either the computer's own internal data sources, or external sources connected to the system. The catalogue number is used to refer to a directory which the computer 138 calls up from, for example, magnetic disc storage. Such indirect add~ allows more flexibility in the operation of the system. Internal data sources may be, for example, magnetic disc and tape 137, or still pictures in the form of slides 139. The dsta retrievable by this system may be stored in either analog or digital form. After lo~ ~tine and copying the selected data, central computer 138 decodes it, if it is stored as teletext (in digital form), to an analog (NTSC) "scene," and 1'~0~89~) arranges it in the proper format for display on a television screen. If it is already stored in analog form, the deco~ling is unnecessary. Data stored in the computer's local sources will preferably be stored with the catalogue number already in the vertical bl~nkinE interval (VBI). If it is not there, the central computer 138 inserts the catalogue number into the VBI before tr~nimi~ion. Although in the preferred embodiment ~e VBI is used to carry the catalogue number, it will be appreciated that this number may be placed anywhere in the tr~n~mi~ion. The selected data and its catalogue number are then sent to the head end 100 which transmits them the appropriate number of times along the trunk line 102 to the bridger amplifier 104 and control station 140.
Although in the preferred embodiment the station identification number is not used by central computer 138 to control data flow, because the catalogue number is used by the control station 140 to determine which subscriber should receive $he data, it is possible for computer 138 to make use of the station identification number in other ways. For example, it may be used by $he computer to determine which control station 140 requested the data and thereupon to attach $o the data an additional signal which will "alert" that control station to the fact that data is arriving for one of its subscribers. Also, whereas in the preferred embodiment all requested information is transmitted along all trunk lines, the station identification number may be used to select the proper trunk line for data tr~n~mi~sion~ thereby reducing unnecessary traffic on the other lines. Furthermore, if it is desired to charge subscribers for data requests, or if statistics of such requests are to be kept, the station identification number will be needed by central computer 138. Head end 100 need transmit a black-and-white frame only once. If it is transmitting a color frame, that need be transmitted only once if a frame grabber is used which will grab a single color frame. However, with the particular frame grabber used in this system, color frames must be transmitted three times because the presently svailable frame grabber grabs the three colors serially.
Referring now to Fig. 7, a control station 140 is associated with each bridger amplifier 104 to direct selected data to the proper subscriber. Each control station 140 includes an upstream demodulator 1'~03890 142, a downstream demodulator 144, a frame grabber 146, a mini-computer 148, several frame stores 150 (each of which includes a digital-to-analog (D/A) converter 152~, and a modulator 154 for each subscriber. Also part of the control station are two switching circuits controlled by the mini-computer, one switching circuit 156 determining which frame store receives the output of the frame grabber, and the other 158 determining to which modulator the output of the frame stores is sent. The number of frame stores lS0 inclu~led in the control station 140 need not be as large as the number of modlllRtors; only enough frame stores are needed to handle the peak volume of data requests.
Upstream demodulator 142, which is a conventional unit, receives and demodulates data requests from subscribers on a return channel within the range of 6 to 30 MHz. When the arithmetic and logic unit (ALU) of mini-computer 148 detects an output from demodulator 142, it stores it in the mini-computer's RAM. This information, it will be recalled, consists of a station identification number and a catalogue number. The catalogue number in the RAM will be compared by the mini-computer to the catalogue numbers in all of the VBI's of frames arriving on trunk line 102. If a match is found, the frame will be grabbed. The station identification number will be used by the mini-computer to direct the output of the ~p~op.;ate frame store lS0 to the proper subscriber's mod~llator 154, by controlling switching circuit 158.
All analog frames arriving at control station 140 from trunk line lQ2 on the VHF d~ r.,am channel are demo~ ted by do..l~stream tor 144, also a conventional unit. From there, they are sent to both the mini-computer 148 and the frame grabber 146. In the absence of instruction from mini computer 148, switchiry~ circuit 156 is open with respect to all frame stores 150, and the frame grabber 146 does not grab frames. Mini-computer 148 e~ n~s every VBI, comparing the catslogue numbers in the intervals to ~e catalogue numbers stored in its RAM. Whenever a match is found, the mini~omputer 148 signals frame grabber 146 to retrieve the ~1enQdl~l~ted frame and at the same time operates switching circuit 156 so as to direct the frame with that catalogue number to one of the frame stores 150. Also at the same lZ0~8~0 time, the mini-computer operates switching circuit 158, in accordance with the station identification number stored along with the catalogue number, so as to direct the output of the same frame store to the modulator 154 co.,~:po~ to the subscriber who requested the data.
The frame grabber is released to enable it to grab subsequent frsmes.
Becfll~ce the frame stores lS0 store frames in digiW form in RAMs, whereas only analog information can be received on subscribers' television sets, a D/A converter 152 is a part of each frame store 150 and csuses the digitally-stored frame to be converted to analog form before being output. In order to make the frames available to the frame stores 150 in digital form, frame grabber 146 includes an A/D
converter at its input.
Analog data is then used by each mcd~ tor 154 to modulate a unique UHF carrier frequency ~sociated with the television set of the subscriber who requested the data. The n~od~ ted carrier occupies a channel of frequenci~ adjacent the carrier frequency CG- . e;pu~ E to the subscriber's dedicated UHF television ch~nn~?l The data, in the form of a mod ~l~ted UHF carrier, then is sent to combiner 160 where it is combined with VHF signals which are also traveling do~ tream and placed on feeder line 106 for reception by the re~sling subscriber.
The frsme grabber 146 is a commercially-available device r~r- f~tured by Matrox Electronic Systems, Ltd., Montreal, Que. It is capable of ~.s~bL.g a color frame and v-lt~ulli~g it in real time, although it stores the three colors serially and separately. The Matrox frame grabber in^lu~ the ~ ry A/D converter, loE~ic, and memory to perform its functions. Switching circuits 156 and 158 may be, for eYnr~ple~ conventional ~ o ,~bar switching arrangements using pen diodes as the i,.divi~sl switches. The control ststion's mini-computer, although not itself a ccr.. er.lional unit, is built in a conventional manner from st -' rd logic and memory cards.
At each subscriber l~eti 3n~ as shown in Pig. S, one or more b -- ipr-s filters are connected t~ c,. the feeder line 106 and the television set 110. If telo. '- programming is to be received on a d~ ~Feed VHF c - -1, a VHF b~andpass filter 108 is in~lu(led- To 12038~) receive selected data on a dedicated UHF channel, the subscriber will require a UHF bpn~lracs filter 132. These UHF ~n~lp&~, filters block all frequencies except the UHF channel assigned or dedicated to the particular subscriber.
Subscribers to the cable television information system of the present invention are able to receive selected data on a standard, unmodified television set 110, as long as the set is able to receive UHF
hannf~l~ 14 through 83 (470 to 890 MHz). In order to receive information which has already been requested ~nd is being transmitted along the feeder line, the subscriber must tune his television set to his dedicated UHF ch~nn-ol If it is tuned to any other UHF channel, b~dr~ filter 132 will block any signals which may be arriving on that çh~nn~l, and the television set will receive nothing. Only when the subscriber's television set 110 is tuned to his dedicated UHF information channel will selected data be received.
If the number of subscribers on a given feeder line exceeds 70, the number of standard UHF ch-qnnel~, more subscribers can be added to the same feeder line by using non-standard UHF channels and even extending the spectrum into the VHF range. In Fig. 8, for example, an embodiment of this invention is shown in which 1400 subscribers are served by a single bridger amplifier snd control station. If all of the frequencies from 50 through 890 MHz are sllocated to dedicated informstion r~ -nnel~ 140 6-MHz ~h- _lA are available for assignment to subscribers. Using ten feeder lines and col,l.ecting 140 subscribers to each, 1400 subscribers can be served. It should be emphasized, hGl,.e.er, that television programming could not be received on standard VHF ~hr~n ~ in this embodiment without the use of separate feeder lines for programming. Here, all chAnnelc from 50 to 890 MHz are dedicated to information; the standard VHF television l~h~nnPl~ fall within this rsnge (see Fig. 1) and therefore would be used for data reception rather than programming. Separate feeder lines 106 must be used for television programming.
Fig. 9 shows the choice bet-.een using one or two feeder lines 106 -- one of the feeder lines is shown as a dashed line and the other as 8 solid line. In systems using a single feeder line 106 for both data and television programming ("s~me feeder~ systems), the dashed feeder line would not be present. Both feeder lines would be presen$ in systems using separP,te feeder lines 106 for data and programming ("separate feeder" systems).
Fig. 9 also illustrates the inverted spectrum feature of this invention. RPntlr~cs filter 136, which is connected between the feeder line 106 and the television set 110 belonging to subscriber A, is tuned to UHF channel 83, the highest-frequency UHF channel, because subscriber A is locsted closer to the bridger amplifier and control station than any other subscriber. Bec~ce higher frequency signals attenuate to a much grester degree with distance along the feeder line than lower frequency signals, channels of descending frequency sre allocated to subscribers of increasing distance from the bridger amplifier and control station. Since subscriber B is more distant than subscriber A from the bridger amplifier and control station, it is acsigned a lower frequency UHF chRnn~ol, channel 82. Subscriber C, farther still, has UHF channel 81. A similar allocation of chnnneh iS made for the remainder of the subscribers connected to feeder line 106.
Set-top converters 162, which are also shown in Fig. 8, are used whenever the subscriber's dedicated information channel (or television programming rh~nn~l) is not one of the standard VHF or UHF television channels a through 83. In that case, an unmodified television set 110 is unable to receive the dedicated channel unless it is converted to one of the standard rhFtnn~lc. Each subscriber's converter 162 need only convert one channel--his dedicated channel-- to a standard television channel (two converters would be reguired, of course, if both the subscriber's dedicated information channel ~nd his dedicated programming channel were non-standard).
In Figs. 10 md 11, the number of available chPnnel~ in the same feeder system of Figure 9 is compared to the number of available chPnn~lq in the separate feeder system by showing the allocation of the ele~;t~....agnetic spectrum. In both figures, shaded areas are those chP~ Pl~ for which a set-top converter 162 is reguired. ~ Fig. 10, the ~oss hatched area ~abelled "possible overlap't) indicates ~h~nn~h which may or may not already be dedicated to television programming in the 1;~03890 particular cable television system under consideration. If dedicated to programming, they are unavailable for data trAncmi~ion. There are 42 possible channels between 216 and 470 MHz. In a 21-channel cable television system, none of these are used for programming, so all 42 could be dedicated to data. A 35-channel cable television system adds 14 programming channels to the 21-channel system by using the VHF
frequencies from 216 to 300 MHz. In such a system, only 28 information channels would be available below 470 MHz. The area labelled "overlap with entertainment" indicates channe]s which normally would be used for programming in any given cable television system. There is no possible overlap with entertainment in separate feeder systems (as shown in Fig.
11).
Figs. 12 and 13 illustrate the program steps performed by central computer 138 and mini-computer 148, respectively, during the operation of the invention.
Although illustrative embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments and that various changes or modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention. For example, the highest frequency used for dedicsted subscriber rh~nn~l~ should not be considered as limited to UHF channel 83 (884 to 890 MHz) but may be as high as the state of the art will allow.

Claims (35)

CLAIMS:

1. A cable television information system for transmitting video picture information to television receivers at subscriber terminals on a cable distribution system, said cable distribution system including a head end, at least one trunk line connected to said head end, at least one bridger amplifier connected to said trunk line and at least one feeder cable connected between said bridger amplifier and said subscriber terminals, said cable television information system comprising:
information storage means for storing video picture information;
information retrieval means coupled to said head end and said information storage means for retrieving video picture information from said information storage means and supplying the video picture information to said head end for transmission on said trunk lines of said cable distribution system;
control means associated with at least one of said bridger amplifiers and at least one of said feeder lines for capturing and storing the video picture information on said trunk line, said control means including transmission means for transmitting the video picture information to one of said subscriber terminals on a television channel dedicated to said one subscriber terminal.

2. The cable television information system of claim 1 wherein the video picture information comprises standard television photo images.

3. The cable television information system of claim 1 wherein the video picture information comprises still pictures.

4. The cable television information system of claims 2 or 3 wherein said transmission means of said control means transmits the video picture information to said one subscriber terminal at a rate greater than or equal to 30 times per second.

5. The cable television information system of claim 1 wherein said control means comprises a frame grabber coupled to said bridger amplifier for capturing a video frame of the video picture information and a frame store coupled to said frame grabber for storing the video frame in a storage location assigned to said one subscriber terminal.

6. The cable television information system of claim 5 wherein said transmission means comprises a plurality of television channel modulators coupled to said frame store, said television channel modulators being assigned to transmit different dedicated television channels to each one of said subscriber terminals connected to the feeder line associated with said control means, said television channel modulators further transmitting the video picture information to one of said subscriber terminals on one of the dedicated television channels.

7. The cable television information system of claim 6 wherein said transmission means further comprises a D/A converter coupled between said frame store and said television channel modulators.

8. The cable television information system of claim 6 wherein said television channel modulators are UHF modulators, the dedicated television channels being UHF channels.

9. The cable television information system of claim 6 wherein said television channel modulators are both UHF and VHF modulators, the dedicated television channels being both UHF and VHF channels.

10. The cable television information system of claims 6, 8 or 9 wherein the dedicated television channels are assigned to said subscriber terminals in a descending order depending on the distance of said subscriber terminal from said control means.

11. The cable television information system of claims 6 or 8 wherein the same feeder line transmits both the dedicated television channels and standard television broadcast channels to said subscriber terminals.

12. The cable television information system of claims 6 or 9 wherein a first feeder line transmits the dedicated television channels to said subscriber terminals and a second feeder line transmits standard television broadcast channels to said subscriber terminals.

13. The cable television information system of claim 8 wherein the UHF channels are 6 MHz channels in the UHF frequency spectrum of 470 MHz to 890 MHz.

14. The cable television information system of claim 9 wherein the dedicated television channels are 6 MHz channels in the frequency spectrum of 50 MHz to 890 MHz.

15. The cable television information system of claim 5 wherein said frame store has a plurality of storage locations, one of said storage locations being assigned to each one of said subscriber terminals connected to said feeder line associated with said control means.

16. The cable television information system of claim 1 wherein each of said subscriber terminals comprises a television receiver and channel receiving means coupled to said television receiver for passing the television channel dedicated to said subscriber terminal and blocking all other television channels dedicated to other subscriber terminals.

17. The cable television information system of claim 16 wherein said channel receiving means comprises a bandpass filter for passing the dedicated television channel.

18. The cable television information system of claim 17 wherein said channel receiving means further comprises a filter for passing standard television broadcast channels.

19. The cable television information system of claim 1 wherein said one subscriber terminal comprises request means operable by the subscriber for requesting video picture information selected by the subscriber, said request means generating selection instructions which are transmitted over said cable distribution system to said information retrieval means.

20. The cable television information system of claim 19 wherein said request means comprises a keypad operable by the subscriber to select particular video picture information and signalling means coupled to said keypad for generating the selection instructions in response to operation of said keypad.

21. The cable television information system of claim 20 wherein said signalling means comprises oscillator means for transmitting a signal in the frequency range of 6-30 MHz.

22. The cable television information system of claim 19 wherein the selection instructions include a station identification number identifying said one subscriber terminal.

23. The cable television information system of claims 19 wherein said information retrieval means is responsive to the selection instructions for retrieving the selected video picture information.

24. The cable television information system of claim 23 wherein said information retrieval means further generates address information identifying the selected video picture information and transmits the address information and video picture information to said control means via said head end and trunk lines of said cable distribution system.

25. The cable television information system of claim 24 wherein said control means further includes decoding means coupled to said transmission means for decoding the address information to enable said transmission means to transmit the video picture information on the dedicated television channel assigned to said subscriber terminal requesting the selected video picture information.

26. The cable television information system of claim 25 wherein said information retrieval means is a central computer.

27. The cable television information system of claim 1 wherein said one subscriber terminal comprises request means for generating a request for specified video picture information and transmitting the request on said cable distribution system to said information retrieval means, said information retrieval means being responsive to the request for retrieving the specified video picture information.

28. The cable television information system of claim 27 wherein said request means further generates address information identifying said one subscriber terminal and said information control means is responsive to the address to enable said transmission means to transmit the specified video picture information to said one subscriber terminal requesting the specified video picture information.

29. The cable television information system of claim 28 wherein said information retrieval means is a central computer.

30. The cable television information system of claim 1 wherein said information storage means comprises a digital slide storage device.

31. The cable television information system of claim 1 wherein said information storage means comprises an analog storage device.

32. A cable television information system for transmitting information to television receivers at subscriber terminals on a cable distribution system including a head end, trunk lines connected to said head end, bridger amplifiers connected to said trunk lines and feeder cables connected between said bridger amplifiers and said subscriber terminals, said cable television information system comprising:
information storage means for storing information;
information retrieval means coupled to said head end and said information storage means for retrieving specified information from said information storage means upon request by one of said subscriber terminals, said one subscriber terminal including request means for requesting the specified information and transmitting a request to said information retrieval means over said cable distribution system, said information retrieval means supplying the specified information to said head end for transmission on said trunk lines of said cable distribution system, control means coupled to said trunk lines at a location corresponding to the location of the bridger amplifier and feeder cable associated with said one subscriber terminal for capturing the specified information, said control means including storage means for storing the specified information and transmission means connected to said storage means for repetitively transmitting the specified information stored in said storage means to said one subscriber terminal on a television channel dedicated to said one subscriber terminal.

33. In a cable distribution system including a head end, trunk lines connected to said head end, bridger amplifiers connected to said trunk lines, feeder cables connected to said bridger amplifiers and subscriber terminals connected to said feeder cables, a cable television information system for transmitting video picture information to television receivers at said subscriber terminals, said cable television information system comprising:
information storage means for storing video picture information;
information retrieval means coupled to said head end and said information storage means for retrieving video picture information from said information storage means upon request by one of said subscriber terminals and supplying the video picture information to said head end for transmission on said trunk lines of said cable distribution system;
control means coupled to said trunk lines at a location corresponding to the location of the bridger amplifier connected to the feeder line connected to said one subscriber terminal for capturing the video picture information, said control means including storage means for storing the video picture information and transmission means coupled to said storage means for repetitively transmitting the video picture information stored in said storage means to said one subscriber terminal on a television channel dedicated to said one subscriber terminal.

34. A television information system for transmitt-ing video picture information to television receivers at subscriber terminals on a distribution system, said distribution system including a head end and at least one feeder line connected between said head end and said subscriber terminals, said television information system comprising:
information storage means for storing video picture information;
information retrieval means coupled to said information storage means for retrieving video picture information from said information storage means;
control means connected to said information retrieval means and said feeder line for capturing and storing the video picture information retrieved by said information retrieval means, said control means including transmission means for transmitting the video picture information along said feeder line to one of said subscriber terminals on a television channel dedicated to said one subscriber terminal.

35. A television information system for transmitting information to television receivers at subscriber terminals on a distribution system including a head end and feeder lines connected between said head end and said subscriber terminals, said television information system comprising:
information storage means for storing information;
information retrieval means coupled to said head end and said information storage means for retrieving specified information from said information storage means upon request by one of said subscriber terminals, said one subscriber terminal including request means for requesting the specified information and transmitting a request to said information retrieval means over said distribution system; and control means coupled to said information retrieval means and said feeder line associated with said one subscriber terminal for capturing the specified information from said information retrieval means, said control means including storage means for storing the specified information and transmission means connected to said storage means for repetitively transmitting the specified information stored in said storage means along said feeder line to said one subscriber terminal on a television channel dedicated to said one subscriber terminal.