PCT
`INTERL"fATIONAL .APPLICATION PUBliSHED tJNDER THE PATENT COOPERATION TREATY (Pen
`
`WORLD INTELLECTUAL PROPERTYORGA..'{!ZATION
`(ntemational B ure:1u
`
`(51) international Patent Cl:J.ssification 3:
`
`(11) International Publication Number: WO 81/02961
`
`H04N 7/16, 7/04 ·
`
`{43) [nternational Publication Date: 15 October 1981 (15.10.81)
`
`(21) Jnte=tional Appllc>tion Number.
`
`(22) Internntional Filing Date:
`
`(72) Inrentors; :md
`{75) inrencors/Applic:mts (for US oniy): CA:.'vfPBELL. John,
`G. [US/US]; 601 West Non:hgace, Irv·ing, TX 75062
`(US). SCHOENEBERGER, Carl, F. [US/USJ; 2032
`Christie Lane, Carrollton. TX 75007 (US). Bu?-1'- ,
`DENS. Allan. B. [US/US]; 1831 Clear Creek Lane. ·
`Carrollton. TX 7 5007 (US). FOGLE, Rlchard . .YL (USi ;
`US]: 2013 Knoxville Drive. Bedford, TX 76021 (US). ,
`LEMBURG, Joh.ri. R. [US/US]; 512 Le:dngcon L:me, ,
`Richardson, TX 75080 (tiS).
`
`;
`(7.:1) Agents: THUR..\IL'\.:."l'. Ronald. V. eta!.; Hubbard. Thur- '
`man. Turner. Tucker & Giuser, 1200 North Dallas
`Bank Tower.L.BJ Freeway at Preston Road. Dallas. IX
`i52JO (t:S).
`
`(81) Designated States: AT (European patent), CH (Euro(cid:173)
`pe:ln patent!, DE !European p:!.tentl, fR !European .
`oatentl. GB ( Eurooean oacentl. JP. LU (Eurooean oa(cid:173)
`tentl. >iL lE!.!rope.:m p~tentl. Sc i:Europoean.pare~tl.
`cs.
`
`PCT/US8!/004!41
`31 March 1981 (31.03.81) I
`I
`135,987 I
`31 March 1980 (31.03.80) I
`us l
`I
`I
`135.987 (CIP) !
`!
`(71) Applicant (jor all designated Stares e."Ccepr US): TOCOM. :
`INC. [US/.US]; P.O. Box 47066. Dallas. TX 75247 !
`.
`w~
`
`(31) Priority Application Number:
`
`(32) Priority Date:
`
`(33) Priority Counrry:
`
`(60) Parent Application or Grant
`(63) Related by Continuation
`us
`
`Published
`Wich intemaclollai ~·earch reporr
`
`(54) Title: .-\DDRESSA.BLE CABLE TELEv1SION CONTROL SYSTEM wrrn: viDEO FOR.\fAT DATA
`·· IRAl'fSMISSION
`__ .. ·- ..
`
`c.:.. TV
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`SAMPLS:
`
`113
`
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`J EXTRACTOR L/14
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`I
`
`Y,_. 117
`104 J
`LOGIC
`/
`CCMMANO
`r---'-----"-~-"-'-r LEVEL MUTE /SPECIAL
`'------trl
`CONVERTER
`TCNE:S
`CONTROL
`LCOIC UNIT
`SCR::::N CCNT;;~OL
`LlA7A
`
`AUDIO/
`LEVEL
`MUTE
`CONTROL
`
`122
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`t.UOIO
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`/:30
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`/46
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`/44
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`rz,.r4:z
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`APPLE EX. 1023
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`{57) Abstract
`
`An addressable cable television control system controls television program and dara. signal transmission from a centra.
`sra.tion (11) to a plurality of user sra.tions. The data signals include both control and text signals in video line format which are in(cid:173)
`serted on the vertical interval of the television signals, thereby freeing all channels for transmission ofboth television and dar.;:
`signals. ~{oreover, full-channel teletext data in video line format may be transmitted on dedicated next channels with the modi·
`fication of only he:J.d end processors (16). An intelligent converter ( 40) at each remote user location uses the data signals to con(cid:173)
`trol access to the system on the basis of channel, tier of service, special event and program subject matter. The convener uses::.
`graphics display generator (118) to generate display signals for the presentation of the text data on the television receiver (36.
`and for the generation of predetermined messages for the viewer concerning access. emergencies and ocher tlmctions. The con(cid:173)
`vener processes vertical interval text data and selected full-channel text data. boch transmitted in video line format rne kev.
`board of the subscriber (146. 168) provides a number of different functional inputs for the subscriber to interface with the sy.
`stem. The convener ( 40) also includes apparatus for interfacing with two-way interactive dara acquisition and conrrol systems
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international appli(cid:173)
`cations under the PCT.
`
`AT
`AU
`BR
`cr
`CG
`CH
`at
`DE
`OK
`n
`fR
`GA
`GB
`HU
`JP
`
`Austria
`AUstralia
`BnZII
`Cc::ntral Airic:1n Republic
`Congo·
`Swio:erl:lnd
`CJrneroon
`Ciennany • .F:deral Rc:puoli.:: ot
`Denmark:
`' Finland
`Ft:~nce
`Gabon
`United Kingdom
`HunY£ry
`Japan
`
`KP
`LI
`LU
`."rtC
`)1G
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`RO
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`SN
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`Democratic P:ople's Re;:uoli;: oiK.:~rea
`Liechtenstein
`L uxc::rnoourg
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`Madagas.::::~r
`:vtalawi
`~ eth-=rl:mds
`~orway
`Romania
`Sweden
`S<!negal
`Soviet Union
`Chad
`Togo
`United States oi Ameri.::::~
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`WU Ul/U:l<J6l
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`PCT/uSBl/00-J.l-J.
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`1
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`ADDRESSABLE CABLE TELEVISION CONTROL SYSTEM WITH
`VIDEO FOR:\\A T DATA TRANSMISSION
`
`CROSS REFERENCE TO REL."\ TED AP?LICA TION
`
`This
`
`is a c.ominuatlon-in-part application of our prior co-
`
`5
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`pending application, U.S. Serial No. 06/135,987, filed ~larch 31, 1980.
`
`s . .:..cKGROCi'!D OF THE [NVENTION
`This in·,em:1on relat:es -.:o an addressable c=.b!e television comrol
`
`sys-;:em.
`
`:Vlore par-;:iculc..rly: 'the presem: invention relates to a c=.cle
`
`television sys;:em having a mul dple-function addressable convener and
`
`10
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`including da1:a transmission in video format during the ven:ic2.1 .interval
`of the video field or during subs!antially the entire video field.
`
`In recem years, the ava.ilabill ty of cable 'television programs
`
`and services for
`
`the general public has expanded rapid! y.
`
`Com(cid:173)
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`munication satellites have enabled nationwide programming for a
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`15
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`number of 11Super stations". Sophlstica ted two-way interactive cable
`
`communlca!lon systems have laid the groundwork for a wide speccrum
`
`of cable television and data communication services for the consuming
`
`public. After years of development, cable television systems have been
`
`or are now being
`
`installed in many major cities to provide the
`
`20
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`television consumer with a vast array of programming choices as well
`
`as many other services which can be utilized at home: such as
`
`shopping, banking and schooling. Other services Qrov.ided by such
`·systems incude home security moniToring, medical and emergency
`
`alen signaling and information retrieval.
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`25
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`In order
`
`to provide
`
`these new services and programs in a
`
`sys-cematic and efficient manner' generc:dized control sys-;:ems are
`required which can supervise access w both one-way anc two-way
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`APPLE EX. 1023
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`2
`sophisticated cable communication systems having different degrees of
`complexity. Control is required to differentiate and limit access on
`several bases, including different levels or tiers of subscribers to
`
`5
`
`different television channels, and different programs and events on a
`In addition, for many subscribers it is desirable to be
`given channel.
`able to limit access to certain programs because of the program
`subject matter. Presently, there are no cable systems having this
`degree of sophistication in controlling program access. Even simpler
`
`15
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`20
`
`conventional cable systems which provide for limiting program access
`10 must be two-way interactive systems requiring more complex and
`expensive equipment than one-way sys~:ems.
`Besides this problem of coordinaring cable communications, rhe
`the
`transmission of data has become
`ln-
`for efficiency in
`need
`creasingly apparent. Athough approximately 55 video and sound
`channels are presently available between
`the allocated
`television
`frequencies of 50 and 4-00 megahertz, the varied types of possible
`cable television programming and data !ransmission services req'uire
`::he efficient utiliza~:ion of ;:hese frequencies.
`For exc.mple, cable
`television programming includes movies, specic.l events, news, con-
`sumer programming, community access and religious progr2.mm!ng. An
`almosi: limitless range ·of data can be provided, including repon:s on
`swck and money markets, weather reports, airline schedules, shopping
`direci:ories, enten:ainment schedules, ~:raffle reports, home security
`data emergency and first aid informa1:ion and unlimited library -;:ex~:ual
`information. The possibility
`for cable system operators
`to
`lease
`available cable channels to private concerns for
`these and other
`services makes it
`imperative
`that cable
`transmission control be
`efficient and flexible. In order to effectively utilize the avc.ilc.ble
`portion of the electromagnetic spectrum for such a wide varlei:y of
`programming and data transmission, the cable system should be able to
`process the data quickly and efficiently while using relatively simple
`and inexpensive equipment which is affordable to the general con(cid:173)
`suming public.
`
`25
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`30
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`35
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`In the last few years, various experiments have been conducted
`regarding the transmission of data over the vertical blanking imerval
`of' a normal television signal. This interval in the video signal occurs
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`APPLE EX. 1023
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`wo 81/02961
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`PCT/US8l/00-H-+
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`60 times each second as the cathode ray tube beam sweeps from the
`bottom to the top of the TV screen and is relatively unused for the
`transmission of data. Some early systems such as that shown in U.S.
`
`Patent 3,769,579· issued on October 30, 1973, utilized the vertical
`interval for transmitting control signals to individual transponders at
`there has been exper-
`locations. More recently,
`the subscriber
`imentation with television broadcasting systems which transmit visual
`
`data on
`
`the vertical blanking
`
`interval,
`
`referred
`
`to as
`
`teletext
`
`transmission,
`
`for display as pages of
`
`text on suitably equipped
`
`television receivers. These experimental systems have generally been
`limited to over-the-air broadcasting of teletext transmissions for a
`single channel, and
`the necessary apparatus for cable
`television
`systems has been regarded as too complicated c.nd expensive to be
`
`practical when compared to the high-speed transmission of compact
`data over a dedicated channel.
`It is desirable in many instc.nces to dedicc.te_an entire television
`chc.r.:1ei -:o the transmission of ca;:a rather. thc.n video signals. Prior
`art systems far dedicc.!ed da~:a channels
`typicc:..ily require speci:::.i
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`5
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`10
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`15
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`transmitters and receivers different from -chase used for 1:he trans-
`20 mission of video signals in order to c.chieve the desired high baud (bi:s
`per second) rate to eiiiciently u!illze the channel bandwidth. This
`special date. transmission equipment has resulted in substantic.l cost
`
`and complexity, pan:icuic.r!y at each remote user Terminal where a
`different receiver is usuc.lly required for each dedlcc.ted data channel.
`25 A simple and inexpensive system for the high speed transmission of
`data on a dedicated da-ca channel has been greatly needed.
`
`SUMMARY OF THE INVENTION
`The present invention provides a relatively inexpensive and
`simple cable television system having the capability of controlling
`access to a wide range of television program and data signals while
`efflcientl)' transmitting data signals in a video format during the
`vertical interval (VI) of each television program chc.n.nel. This VI dai:a
`
`not only provides comrol data for c.n intelligent converter unit, bur
`also provides a substantial amount of textual da-ce. per channel for use
`either to provide additional data to supplemem a channel
`television
`program or as a separa!e all textual c.nd grc.phic channel.
`
`30
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`35
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`~ "' o-...··--,....·<...i "\
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`-r
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`;-_
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`PCT /USBI/00-t. I .t.
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`4
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`The present invention includes an intelligent addressable con(cid:173)
`verter designed to convert and descramble video for up to 55 CATV
`channels. For dual cable systems, an optional cable switch on the
`converter doubles the available number to 110 channels. The converter
`of the present invention receives control data which allows the system
`operator to control subscription television services on a per channel,
`In addition, the system and
`per service tier, and per event basis.
`converter of the present invention enables each subscriber to define
`his own level of required eligibility based on program subject matter.
`The system of the present invention also enables a com-
`plementary text channel to be transmitted on the vertical interval of
`each of the incoming video signals and to be decoded and displayed as
`an alternate channel to the video programming. The data for the
`complementary text channel is preferably displayed in a combination
`of text and graphics. This capability effectively adds 55 additional
`text channels for a wide spectrum of data-type information for the
`consumer. Thus, the present system provides 110 independent channels
`of television program and text viewing in a one cable system and 220
`channels in two cable systems. Moreover the control system of the
`present invention, when used in conjunction with appropriate two-way
`interactive apparatus, provides a complete two-way interactive com(cid:173)
`munication system
`including pay-per-view, home security, opinion
`polling, channel monitoring, information retrieval, and with additional
`equipment, energy management.
`Moreover, the present Invention provides a relatively inexpen-
`sive and simple cable communication system having the capability of
`transmitting data signals in a video format over substantially the
`entire video field of selected
`television program channels.
`By
`transmitting data in the video format over these dedicated data
`channels,
`the present
`invention minimizes
`the need
`for special
`additional expensive equipment, particularly special data receiver
`equipment
`for each converter unit.
`Rather, each addressable
`converter of the present invention is readily adap,ted to receiving
`selected lines of data transmitted in video format without requiring
`additional expensive receiver equipmem:.
`For a better understanding of the present invention, together
`with other and further objects and features thereof, reference is made
`
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`wo 81/02961
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`PCT/US8l/00-H4
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`5
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`to
`
`the
`
`following description
`
`taken
`
`in connection with
`
`the ac(cid:173)
`
`companying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIGURE 1
`is a simplified block diagram of a preferred
`
`5
`
`embodiment of the addressable cable television control system of the
`
`present invention;
`FIGURE 2 is a block diagram of a preferred embodiment of the
`head end portion of the system shown in Figure l;
`FIGURE 2A is a diagram showing the line layout of a video
`
`10
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`15
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`20
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`· 25
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`field according to the pr.esent invention;
`FIGURE 2B is a time-based diagram showing the video line
`format of data transmission in accordance with the present invention; .
`FIGURE 3 is a block diagram of the programming control
`system shown in Figure 2;
`FIGURE 4 is a block diagram of the head end video processor
`shown in Figure 2;
`FIGURE 5 is a more detailed block diagram of the head end
`video processor of Figure 4;
`FIGURE 6 is a block diagram of a preferred embodiment of the
`addressable converter of the present invention shown in Figure 1;
`FIGURE 7 is a block diagram of the converter control logic
`shown in Figure 6;
`FIGURE 8 is a block diagram of the VI data extractor unit
`shown ln Figure 5;
`two
`FIGURES 9 and 10 are schematic diagrams showing
`preferred methods of connecting the converter of Figure 6 in a CATV
`system;
`FIGURE 11 ls a schematic diagram showing the data format for
`the system of the present invention;
`FIGURE 12 is a flow diagram showing the operation of the
`converter shown in Figure 6;
`
`.
`FIGURE 13 is' a top plan view of the keyboard of the converter
`of Figure 6;
`
`.
`
`35
`
`FIGURE 14 is a diagram showing a video layout for full-channel
`teletext data transmission in accordance with another embodiment of
`the present invention;
`
`APPLE EX. 1023
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`PCT/USSI/00414
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`6
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`FIGURE 15 is a block diagram for the preferred embodiment of
`FIGURE 14 of the head end portion of the system shown in FIGURE
`1· '
`
`FIGURE 16 is a block diagram of the screen composition system
`and selective data retrieval system shown in FIGURE 15; and
`FIGURE 17 is a flow diagram showing the operation of the
`converter shown in FIGURE 16 operating in conjunction with the head
`end of FIGURE 15.
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`20
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`DETAILED DESCRIPTION
`FIGURE 1 shows a simplified block diagram of a one-way cable
`television system 10 in accordance with the present invention. A head
`includes a central data system 12 utilizing a control
`end station 11
`computer which gathers data from a wide variety of sources and
`formats the data for 1:ransmlssion on video frequency channels. The
`central da;:a control system preferably has a two-way imerface !ink 13
`with a remote compurer which may be used for central control and
`billing
`functions.
`The
`formatted data
`is
`then
`transmitted by
`communications link 14 to a television program processor 16 where it
`is incorporated into the vertical blanking intervals of video signals
`generated by a variety of television program sources.
`In addirion, the
`data may be formatted for
`transmission
`in a separate channel
`dedicated only for the transmission of data. The dedicated data
`channel transmissions are connected over link 18 to a head end signal
`combiner 20 where they are combined with a plurality of vid.eo signals
`transmitted from television program systems 16 along transmission link
`22. The head end unit then transmits the combined cable television
`and data signal to remote subscribers. Normally, the signals are then
`transmitted through a cable network, referred to as a cable plant to
`a plurality of subscribers.
`FIGURE 1 shows a single cable plant 30 servicing a plurality of
`cable television subscribers by way of a one-way da'ta link 32. The
`' ~ransmitted signals are received by an addressable converter 40 on a
`one·.:.way data bus 32. Converter 40 then processes the data on line 38
`as determined by subscriber input 34 for desired viewing on one or
`35 more television sets 36.
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`APPLE EX. 1023
`Page 8
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`7
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`Referring now to FIGURE 2, one preferred embodiment of the
`data control system 12 and television program processor
`16 ls shown
`This preferred embodiment which is shown in
`in greater detail.
`FIGURES 2 through 12 concerns a system which transmits data in the
`vertical interval of each video field. Another preferred embodimem
`
`disclosing a full-channel data transmission system using a video format
`will be discussed thereafter.
`As shown in FIGURE 2, a programming control system
`
`(PCS)
`
`50 generates a continuous stream of data that contains a mixture of
`This data
`subscriber addressing signals and channel control signals.
`is transmitted to a plurali-r:y of head end video processors
`(HVP) 52
`and 53 for combining with video signals in a plurality of different
`l?CS 50 is also preferc.bly connected by a t\vo(cid:173)
`channel frequencies.
`way data link to a remote computer for use in various
`control
`
`functions.
`A text forma"L""Cer system 54- receives dc.tc. from a \vide varie-ry
`of 1 scurces such c.s
`·.vec.ther, ne•,t.·s, stock and others which are
`
`formaned fer video transmission and !hen selecTively uansmined !n
`~:ext form 1:0 the piurality of HVP uni""Cs 52, 53. The text formaEe:-
`system 54 preferably is comprised of a plurality of text formaners,
`each processing data from a text or graphics source. A variety oi
`
`manufacturers produce" equipment for cable television digital channels
`which are easily adaptable to the present system. One soL.:rce of
`suitable conventional formatters ls Video Data Systems, Happaque,
`LI., N.Y.
`Video signals are generated for Input to each HVP unit by
`
`conventional sources, either from local video input sources as shown
`for HVP unit 52 or satellite video input sources for HVP unit 53.
`In
`either case, the signals are processed by a conventional channel
`processor 56 having modulator and demodulator units and a standard
`
`head end processor. Each television channel is preferably processed at
`base band video for purposes to be explained later.
`The subscriber addressing and channel control data from PCS 50
`is input to HVP 52 on line 41 where lt Is inserted in the venical
`interval of -che video signal. The channel control data from PCS 50
`is processed at · HVP 52
`to generate scrambler· signals, program
`
`identification signals, tier signals and eligibility code signals as will be
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`APPLE EX. 1023
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`These signals are utilized by each subscriber's
`later.
`discussed
`to determine the particular subscriber's
`addressable converter 40
`authorization to receive each program and to control descrambling of
`the video signals.
`One of the text signals from text formatter 54 is also input to
`HVP 52 on line 39 te_ be inserted into the ven:ical interval of the video
`signal. Preferably,-~ different type of textual data are insen:ed into
`the vertical interval of each video channel so that a complemem:ary
`text channel may be selected by each remote subscriber.
`HVP unit 52
`then routes the base band-video outpur with
`vertical interval data on line 44 w a standard head end modulator and
`From there, the signal is sem w
`processor in processing unit 56.
`master head end unit 20 where it is combined with signals from other
`channel processors to provide the total multiple channel CATV signal
`for ourput on line 21 to the cable plant. An FSK data modulawr 58 is
`connected directly between PCS 50 and head end signal combiner 20
`by line IS for rransmission of data on dedica~:ed data channels.
`In order to understand how a data signal is transmitted on :i":e
`ven:ical interval of a television program signal, the vertical lm:erval of
`a conventional
`television signal will be described.
`Referring to
`FIGURE 2A, each television signal is made up of a series of "lines"
`each of which represent the length of time required for the cathode
`-che
`ray tube of the television set to make one horizontal sweep across
`screen. The number of horizontal lines required to cover the screen
`is called a field 700, and there are two interlocking fields, both having
`262.5 lines which together form a frame., In conventional systems, 30
`frames are transmitted each second. to make up the television picture .
`. Each time the cathode ray tube reaches the bottom ~f the screen it
`must sweep diagonally upward to the top of the screen to begin a new
`field. This 1:ime period 702 is referred to as the "vertical blanking
`interval" or simply "vertical interval" and is normally approxima!ely
`21 lines in length. The television picture 704- begins at about line 21
`and extends 1:0 about line 261, but normally the picture is viewable on
`most television sets only between about lines 25 and 255.
`Although no television picture data is transmitted during !he
`vertical int.erval, the television industry has provided for a number of
`different types of control transmission on certain lines of t:he intervc.J..
`
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`9
`
`In most cases, the first nine lines of the vertical interval are used for
`to 14- are
`Lines 10
`equalizing and for vertical synchronization.
`normally at black level to minimize picture interference on some sets.
`Thus, only lines 15 to 21 are available for data transmission. Lines 15
`and 16 have already been utilized at least experimentally for other
`purposes.
`Lines ·19-21 are normally used for network control in-
`formation for transmission to the receiver sets.
`Thus, lines 17 and 18 are the only ones which are presently
`available for vertical interval data transmission 710 using the invention
`of the present system.
`These two !lnes normally contain network
`testing data to determine proper reception by the hec.d end system.
`Once the television signals have been received, lines 17 and 18 can be
`cleared for passing data to the converters using the present invention.
`It should be understood that if additional lines in the vertical interval
`are cleared
`ln
`the
`furure,
`they could also be used
`for date.
`I trc.nsmlssion in accordance with the present invention.
`?refer:=.bly, the present invemion uses Lines 17 and IS of 1:he
`ven:ical interval to trc.nsml1: both the text data ar.d
`the subscriber
`In one field of a given frame lines
`address and channel control data.
`17 and 18 are used to ~ransmit text data, and in the other frame
`field,
`the subscriber address and channel control data is projected on
`lines
`17 and 18. The present invention also uses line lO which is c.t
`the
`.black
`11Zero 11 voltage
`level of each vertical
`interval for a DC
`reference level 712 for the data signals. This reference signal passes
`to the converter as part of the v~rtica1 interval where it is used as
`a reference level for data extracti.on. This procedure greatly enhances
`the c.ccuracy of the data transmission by automatically compensc:dng
`for any- DC level shift in the vertical interval portion of the television
`signal.
`
`Using the procedure described above an effective text charac(cid:173)
`ter. transfer rate of about 240 characters per second is achieved. This
`is a relatively slow rate compared to some other .methods of data
`transmission. However, since the text may be transmitted over all 55
`televisi.9n program chann~ls the total text available to the user is very
`substantial. Moreover, as previously mentioned, the present invention
`may inclu"de one or more dedicated channels for only text data
`transmission using the 11line" or video format which will be described
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`more fully in FIGURES 2B and 11. By using most of the 525 lines of
`
`each television signal frame for text data transmission a vast quantity
`
`of text can be transmitted and received on a given channel using the
`
`transmitting and receiving· apparatus of the present system.
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`No.
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`special expensive data transmission or receiving equipment is
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`re(cid:173)
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`quired.
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`""'>
`A better understanding of the line or video format of the da-ca
`
`used in the present invention may be obtained b'y reference to FIGURE
`
`2B, which shows a standard timing diagram for a single television line
`of the type shown in FIGURE 2A. This is a standard video line forma!
`in accordance with FCC or NTSC requirements. The amplitude of the
`
`video signal is measured in standard IRE uni1:s.
`
`As shown in the figure, the video signal begins \Vith a nega-cive
`horizontal sync pulse 720 of about 40 IRE units. This pulse establishes
`the beginning point of the horizom:al sweep of the ca-::hode ray tube
`across the screen. Next, a color burst oscillating puls~ 722 occurs
`in c.
`\vhich is normally used to synchronize color decoding ci::-cuiuy
`
`television receiver.
`Data is encoded in the video scan Line 724 following the color·
`burst signal 722 as shown in FIGURE 2B.
`This
`line is normally
`
`composed of 92- bit lm:ervals with each bit being idem:ified as "!" wi~:h
`an ampti1:ude level of 50 to 80 IRE units or "0", carrying an amplitude
`
`of approximately zero IRE units.
`
`In this manner, the sTandard analog
`
`video signal is replaced by a binary digital data packet 726 of 92 bi--cs
`which is transmitted together with the horizontal sync pulse and color
`burst pulse, both of which are analog signals.
`Looking now at FIGURE 3, the programming comrol system 50-
`is shown in greater detail. The heart of PCS 50 is a sophisticated
`control computer, having both a random access memory and a read-
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`30
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`only· memory. Computer 60
`
`is preferably a conventional general
`
`purpose minicomputer utilizing a central data syster::l. Computer 60
`
`may be controlled by a conventional system operator console 62, a real
`
`time dock 64- and external data links 66 including a two-way interface
`
`35
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`with another remote computer for central controL Control compmer
`60 is also connected to magnetic storage devices such as a cartridge
`tape data ·storage unit 68 and a
`floppy disk subsys:em 70 com(cid:173)
`
`municating wil:h control computer 60 over two-way data links 72 and
`
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`Page 12
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`il.l/U,:)Ol/VV...-.J..,.
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`11
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`7'+ respectively. Other outputs to conventional units such as remote
`terminal 7 6 and printer 78 are optional.
`_ One preferred embodiment of control computer 60 comprises a
`rack-mounted Hewlett-Packard 1000 minicomputer system having
`standard operating system software. The computer may also include
`interface with
`twa-way data
`application programs a!~_owing it to
`acquisition and control systems. This interface is preferably carried
`out by communications with the home terminal shown in FIGURE 10.
`The head end video processor unit 52 of FIGURE 2 is shown in
`more detail in FIGURE lf.. A digital control and
`timing unit 80
`receives the text data from text formatter 54- on line 39 and the
`subscriber addressing and channel control data from PCS 50 a.n line lf.l
`and processes it for insertion in the vertical intervc.l of the video
`chc.nnels. The date. on line lf.l loops through unit 80 c.nd bc.ck om on
`line 42 to the next digital control and timing unit. The base band video
`signal is input an line !!J to a video. vertical interval processing unit
`32 where it is ?recessed for inse~-:ior. of -;:he subscriber addressing and
`channel comrol data from unit SO vic.
`two-wc.y dc.t:a link 84. As
`previously described, 1:he data is preferably lnsened on two lines of
`each ven:ical interval and
`then direc-ted
`to a conventional video
`scrambler 86. The resulting video signal which has been loaded with
`data and scrambled
`is !hen connected
`to
`the standard head-end
`processor 56 shown in FIGURE 2.
`Referring now to FIGURE 51 the head end video processor 52
`is
`shown in even greater detail. The digital control and riming unit 80
`includes a dc.tc. forma!ter 88, a sc.rambler controller 90, a sample and
`hold unit 92 and a timing signal generator 9'+. The video
`ven:ical
`imeryal processing unit 82 includes a sync extractor 96 and a video
`switch unit 98.
`The video signal is inpu1: on line '+3 to the sample and hold unit
`92, the sync ex1:ractor 96 and the video switches 98. The text data
`.
`is input to the data formatter 88 an line 39 and the subscriber and
`control data is input on line 41 to data formatter 88 and output on line
`42. The sync extractor unit 96 divides aut the horizontal and ven:ical
`sync si.gnals from the video signal and directs th~m to the timing
`signal generator on line 85. Timing signal generator 94 counts the
`lines of 1:he vertical interval of each field and outputs enabling signals
`at the appropriate time.
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`Page 13
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`12
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`A reference enable signal is output to sample and hold unit 92
`line 95 when "line 10"
`on
`is detected
`interval
`in each vertical
`representing the black "zero" level which is used as· the DC reference
`level. The sample and hold unit then outputs a DC reference signal
`
`5
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`on line 93 to the data formatter so that the incoming data or text can
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`be properly positioned relative to "line 10" of the vertical interval.
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`The properly· formaned data is then output to video swi-cches 98 to
`
`await transmission at the proper time in the venical interval.
`
`When timing signal generator 94 reaches "line 17" in rhe ven:lcal
`interval, a data enable signal is output on lir.e 83 to the video switches
`98. Upon receipt of the data enable signal~ video switches 98 turn off
`the video input and turn on the data input which is passed .:hrough on
`line 81 to the video scrambler unit 86. At the same time, a scramble
`
`disable timing signal is transmined from data formatter 88 on line 89
`I.'!. the scrambler controller 90 \Vhich in -rurn outpu-cs a scramble disable
`~ignal on line 87. This signal enabies the data on line 81
`to pass
`t::rocgh
`the video scrambler and om on
`line 4-4 without being
`
`scrambled. When timing signed generator detects the end of "line 18"
`of the vertical interval, a data disable signal is directed via line 83 w
`the video switches 98 which turn off the data line and turns on the
`video line.
`.-\ t
`the same time, a scramble enable timing signal is
`
`direcred on line 89 to the scrambler controller which transmits a
`
`scramble enable signal to the video scrambler via line 87. This signal
`
`enables video scrambler 86 so that the video signals corning in on line
`81 will be scrambled before _being transmitted on lin