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`ADDRESSABLE CABLE TELEVISION CONTROL SYSTEM WITH
`VERTICAL INTERVAL DATA TRANSMISSION
`
`'
`
`BACKGROUND or THE-INVENTION
`This invention relates to an addressable cable television control
`
`invention relates to a cable
`system. More particularly; the present
`television system having a multiple-function addressable converter and
`including datatransmission during the vertical interval of the video
`data.
`
`In recent years,
`
`the availability of cable television programs
`
`the general public has expanded rapidly. Com-
`and services for
`munication satellites have enabled nationwide programming for a
`number of "super stations". Sophisticated two—way- interactive cable
`communication systems have laid the groundwork for a wide spectrum
`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
`television consumer with a vast array of programming choices as well
`
`as many other services which can be utilized at home, such as
`shoppin nd schooling. Other services. provided by such
`systemsA-i-n-cude- home security ‘monitoring, medical and emergency
`alert signaling and information retrieval.
`In order
`to provide these new services and programs in a
`systematic and efficientmanner, generalized control systems are
`required which can supervise access to both cne—way and two-way
`
`5
`
`10
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`15
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`
`20
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`sophisticated cable communication systems having different degrees of
`complexity. Control
`is ret]ni_red'to differentiate and limit access on
`several bases.
`includingidifferent
`levels or
`tiers ‘of subscribers to
`
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`given channel.
`In addition, for many subscribers it is desirable to be
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`able to" limit access to certain programs because of the program
`subject matter.
`Presently,
`there are no cable systems having this
`degree ofsophistication in controlling program access. Even simpler
`
`conventional cable systems which provide for limiting program access
`must be two-way interactive systems requiring more complex and
`expensive equipment than one-way systems.
`I
`Besides this problem of coordinating cable ‘communications, the
`need for efficiency in the transmission of data has become in-
`creasingly apparent.
`Athough approximately 55 video and sound
`channels are presently available between the allocated television
`‘frequencies of 50 and 400 megahertz,
`the varied types of "possible
`
`cable television programming and data transmission services require
`the efficient utilization of these frequencies.
`‘For examp1e,.cab1e
`television programming includes movies, special events, news. con-
`
`sumer programming, community access and religious programming. An
`almost limitless range of data can be provided. including. reports on ,
`
`stock and money" markets, weather reports, airline schedules. shopping
`directories, entertainment schedules,
`traffic reports, home security
`data emergency and first aid information and unlimited library textual‘
`information. The possibility for cable system operators to lease
`
`these and. other
`available cable channels to private concerns for
`services makes
`it
`imperative that cable transmission control be
`efficient and flexible. In-order to effectiveiy utilize the available
`portion of’ the electromagnetic spectrum for such a wide variety 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-
`suming public.
`_
`In the last few years. various experiments have been conducted
`- regarding the transmission of data over the vertical blanking interval
`of a normal television signal. This interval in the video signal occurs
`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,?69,5'?9 issued on October 3{|,‘l!-J73, utilized the vertical
`interval for transmittingueontrol signals to individual transponders at
`More recently,
`there has been exper-
`the subscriber
`locations.
`imentation with television broadcasting systems which transmit visual
`
`_
`
`ll}
`
`15
`
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`
`25
`
`30
`
`35
`
`2
`
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`
`t
`
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`
`.
`data on the vertical blanking interval,
`
`K
`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 al
`single channel. and the necessary apparatus
`for cable television
`systems has been regarded as too complicated and expensive to be
`practical when compared to the high-speed transmission of compact
`data over a dedicated channel.
`I
`SUMMARY OF THE INVENTION
`
`invention provides a relatively inexpensive and,
`The present
`simple one-way cable television system having the ‘capability of
`controlling access to a wide -range of television program and data
`signals while efficiently. transmitting data signals in the vertical
`interval (VI) of each television program channel. 'l‘his_ VI data not only
`provides control data for an intelligent converter unit. but also
`provides a substantial amount of textual data per channel
`for use
`either to provide additional data to supplement a channel television
`
`program or as a separate all textual and graphic channel.‘
`The present
`invention includes an intelligent addressable con-
`verter designed to convert and descramble video for up to 55 -CATV
`7 channels. For dual cable systems, an optional cable switch on the
`converter doubles the available number to 11!] channels. The converter
`
`of the present invention receives control data which allows the system
`operator to control subscription television services on a per channel,
`per service tier, and per event basis.
`in addition,
`the system and
`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 ltext 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
`
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`I
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`4 .
`interactive apparatus. provides a complete two-way interactive com-
`munication system including pay-per-view, home security. opinion
`polling. channe! monitoring, information retrieval, and with additions!
`equipment, energy management.
`'
`
`For 21 better understanding of the present invention. together
`with other and further objects and features thereof, reference is made
`to the following description taken in connection with the ac-
`
`‘
`_
`companying drawings.
`BRIEF DESCRIPTION or THE DRAWINGS
`
`_
`
`simplified block diagram of . a preferred
`a
`is
`FIGURE 1
`embodiment of the addressable cable television control system of the
`
`I
`present invention;
`FIGURE 2 is a block diagram of a preferred embodiment of the
`head end portion of the system shown in.Figure 1;
`
`FIGURE 3 '1s a block diagram of the programrning control
`- system shown in Figure 2;
`FIGURE 4 is a block diagram of the head endvideo 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 apreferred embodiment of the
`
`addressable converter of the present invention shown in Figure 1;
`FIGURE 1'
`is a block diagram of the converter control logic
`shown in Figure 6;
`FIGURE B
`is a block diagram of the VI data extractor unit
`shown in Figure 5;
`.
`-
`‘
`FIGURES 9
`and 10 are schematic diagrams
`
`showing two
`
`preferred methods of connecting the converter of Figure 6 "in a CATV
`system;
`I
`I
`FIGURE 11
`is a schematic diagram showing the data format for
`the system of the present invention;
`F_lGURE 12
`is a flow dlag'ram'showing' the operation of the
`converter shown in Figure 6; and
`
`ID
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`15
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`20
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`25
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`3|]
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`35
`
`_ FIGURE 13 is a top plan view of the keyboard of the converter
`- of Figure 6.
`
`-\-q.
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`
`4
`
`

`
`DETAILED DESCRIPTION
`
`PIGURE 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 l2 utilizing a control
`end station 11
`computer which gathers data from a wide variety of sources and
`formats the data for transmission on video frequency channels. The
`central data control system preferably has a two-way interface link 13
`with a remote computer which may be used for central control and
`
`then transmitted by
`formatted data is
`_The
`billing functions.
`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 addition, the
`data may be formatted ffor. 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'combine_d w_ith a pluralityof video signals
`transmitted from television program systems 15 along transmission link
`22.
`‘The head end unit then transmits the combined _cable television
`and data signal to remote subscribers. Normally, thesignals are then
`transmitted through a cable networit, referred to
`a cable plant to
`I
`a plurality of subscribers.
`.
`1
`FIGURE 1 shows a single cable plant 30 servicing a plurality of
`cable television subscribers by way of a one-way data link 32.
`The
`transmitted 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 forldesired viewing on one or
`more television sets 36."
`
`the data control system 12 and
`Referring now to FIGURE 2,
`television program processor 13 are shown in greater detail.
`A
`programming control system. .(PCS}_ 50 generates a continuous stream
`of data that contains a mixture of subscriber addressing signals and
`channel control signals.
`' This data is transmitted to a plurality of
`
`15
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`20
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`25
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`3!}
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`'35
`
`head end video processors (HVP) 52 and 53 for combining with video
`signals in a plurality of different channel frequencies. PCS 50 is also
`preferably connected by a two-way data link to a remote computer for
`use in various control functions.
`'
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`as-.
`
`‘_
`s —
`A text forrnatter system 54 receives data from ewide variety
`sources such as weather, news, stock and others which are
`
`of
`
`formatted for video transmission and then selectively transmitted in
`text form to the plurality of I-WP units 52, 53. The text formatter
`system 54 preferably is comprised of a plurality of text formatters,
`each processing data from a text or graphics source. A variety of
`manufacturers produce equipment for cable television digital channels
`which‘ are easily adaptable to the present system. One source of -
`suitable conventional formatters is Video Data Systems. 1-lappaque,
`L.1., arr.
`'
`'
`to each HVP unit by
`input
`' Video signals are generated for
`conventional sources. either from local video input sources as shown
`for HVP unit 52 or satellite video input sources for I-NP 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 it
`is inserted in the vertical
`interval of the video signal. The channel control data from PCS 50
`is processed at HVP 52 to generate scrambler
`signals, orogrem
`
`identification signals, tier signals and eligibility code signals as will be
`discussed later.
`These signals are utilized by each subscriber's
`
`addressable converter 40 to determine the particular subscriber's
`authorization to receive each program and to control descrarnbling of
`the video signals.
`"
`-
`One of the text signals from text formetter 54 is also input to
`l-WP 52 on line 39 to be inserted into the vertical interval of the video
`signal. Preferably, a different type of textual data are inserted into
`
`the vertical interval of each video channel so that a complementary
`text channel may be selected by each remote subscriber.
`I-[VP unit 52 then routes the base band-video output with
`vertical interval data on line 44 to a standard head end modulator and
`
`is sent to
`From there, the signal
`processor in processing unit 56.
`master head and unit 20 where it is combined with signals from other
`
`channel processors to provide the total multiple channel CATV signal
`for output on line 21 to the cable plant. An FSK data modulator 58 is
`connected directly between PCS 50 and head end signal combiner 20
`by line 13 for transmission of data on dedicated data channels.
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
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`15
`(cid:18)(cid:22)
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`20
`(cid:19)(cid:17)
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`25
`(cid:19)(cid:22)
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`30
`(cid:20)(cid:17)
`
`35
`(cid:20)(cid:22)
`
`6
`
`

`
`.,T__._
`
`-2-...‘
`
`Looking now at FIGURE 3, the programming control 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-
`only memory.
`Computer
`613
`is preferably a conventional general
`
`(cid:22)
`
`purpose minicomputer utilizing a central data system. Computer 60
`may be controlled by a conventional system operator console 62, a real
`time clock 64 and external data links 66 including a two-way interface
`
`10
`(cid:18)(cid:17)
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`15
`(cid:18)(cid:22)
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`20
`(cid:19)(cid:17)
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`25
`(cid:19)(cid:22)
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`30
`(cid:20)(cid:17)
`
`with another remote computer for central control. Control computer
`50 is also connected to magnetic storage devicessuch as a cartridge
`tape data storage unit 68 and a floppy disk -subsystem 70 com-
`_ municating with control computer 60 over two-way data links 1'2 and
`74 respectively. Other outputs to conventional units such as remote
`
`I
`terminal TB and printer '38 are optional.
`One preferred embodiment of control computer 50 comprises a
`
`rack-mounted Hewlett-Packard 1000
`
`rninicomputer
`
`system having
`
`standard operating system software. The computer may also include
`application programs allowing it
`to inter-i'ace_ with two-way data
`acquisition and control systems. This interface is preferably carried
`out by communications with the home terminal shown in FIGURE 10.
`
`The head and video processor unit 52 of FIGURE 2 is shown in
`
`A digital control and timing'unit 80
`in FIGURE 4.
`more detail
`receives the text data from text formatter 54 on line 39 and the
`subscriber addressing and channel control data from PCS 50 on line 41
`and processes it
`for insertionin the vertical
`interval of the video
`channels. The data on line 4l1oops.tl-trough unit 80 and back out on
`line 42 to the next digital control and timing unit. The base band video
`signal
`is input on line 43 to a video vertical interval processing unit
`82 wi1ere'it is processed for insertion of the subscriber addressing and
`channel control data from unit
`80 via
`two-way data link 84.
`Preferably the data is inserted on two lines of each vertical interval
`and then directed to a conventionalvideo scrambler BE. _ The resulting
`video signal which has been Ioadedwith data and scrambled is then
`connected to the-standard head-end processor 56'shown in FIGURE 2.
`
`we
`
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`
`7
`
`

`
`8.
`
`In order to understand how a"-data signal is transmitted on the
`vertical interval of a television program signal‘, the vertical interval of
`a conventional
`television signal will be described.
`Each television
`signal is made up of a series of "lines" each of which represent the
`length of time required for the cathode ray tube of the television set i
`to make one horizontal sweep across the screen.
`The number of
`
`lines required to cover the screen is calledta field, and
`horizontal
`‘there are two interlocking fields, both having 262.5 lines which
`
`in conventional systems, 30 frames are
`form a frame.
`together
`transmitted each second to make up the television picture.‘ Each time
`
`the cathode ray tube reaches the bottom of the screen it must sweep
`diagonally upward to the top of the screen to begin a new field. This
`
`time period is referred to as the "vertical blanking interval" or simply
`"vertical interval" and is normally approximately 21 lines in length.
`Although no television picture data istransmitted during this time. the
`television industry has provided for a number of different
`types of
`control transmission on certains lines of the interval.
`In most cases, the first nine lines of the vertical interval are
`
`used for equalizing and for vertical synchronization. Lines 10 to 14 are
`normally at blackllevel to minimize picture interference on some sets.-
`Thus, only lines 15 to 21 are available for data transmimion.
`Line.-3.15
`
`and 16 have already been utilized at least experimentally for other
`purposes.
`Lines’!!!-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 data transmission
`using the invention of the present system. These two lines normally
`contain network testing data to determine proper reception by the
`head end system. Once the televisiontsignals have been received. lines
`17 and 18 can be cleared for passing data to' the converters using the
`
`It should be understood that if additional lines in
`present invention.
`the vertical interval are cleared in the future, they could also be used
`for data transmission in accordance with the present invention.
`
`The present invention uses line 17 and 18 of the vertical interval
`to transmit both the text data and the subscriber address and channel
`control data.
`In one field of a given frame lines 17 and 18 are used
`to transmit
`text data, and in the other frame field.
`the subscriber
`address and channel control data is projected on lines 17 and 18. The
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
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`15
`(cid:18)(cid:22)
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`20
`(cid:19)(cid:17)
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`25
`(cid:19)(cid:22)
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`30
`(cid:20)(cid:17)
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`35
`(cid:20)(cid:22)
`
`i‘V?
`
`'3?
`
`-rub
`
`1%
`
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`
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`9
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
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`15
`(cid:18)(cid:22)
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`20
`(cid:19)(cid:17)
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`25
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`30
`(cid:20)(cid:17)
`
`present invention also uses line 1|} which is at the black "zero" voltage
`level of each vertical interval for a DC reference level for the data
`signals. This reference signal passes to the converter as part of the
`vertical
`interval where it
`is used as a reference level
`for data
`extraction. This procedure greatly enhances the accuracy of the data
`transmission by automatically compensating for any DC level shift in
`the vertical interval portion of the television signal.
`Using the procedure described above an effective text charac-
`ter transfer rate of about'24fl 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
`television program channels the total text available to the user is very
`substantial. Moreover,.as previously mentioned, the present invention
`may include one or more dedicated channels for only text data
`transmission using the "line" format which will be described more fully
`
`in FIGURE 11.‘ By using most of the 5,25 lines of each television signal
`frame for text data transmission avast quantity of text can be
`transmitted and received on a given channel using the transmitting and
`receiving apparatus of the present systeni. No special expensive data
`transmission equipment
`is required. Referring now to FIGURE 5,-the
`
`head end video processor 52 is shown in greater detail. The digital
`control and timing unit 80 includes a data formatter 33, a scrambler
`"controller 90, a sample and hold unit 92 and a timing signal generator
`94.
`‘The video vertical
`interval processing unit‘82 includes a sync
`extractor as anda video_switch unit -98.
`The video signal is input on line 43 to the sample and hold unit
`92, the sync extractor 96 and the video switches 98. The text data
`is input
`to the data Eormatter 88 on line 39 and the subscriber and
`control data is input on line 41 to data for-matter 88 and "output on line
`42. The sync extractor unit 96 divides out the horizontal and vertical
`
`sync signals from the video signal and directs them to the timing
`signal generator on line 85. Timing signal generator 94 counts the
`
`lines of the vertical interval of each field and outputs enabling-signals
`at the appropriate time.
`
`9
`
`

`
`.-._c--
`10
`
`'
`
`,:
`
`A reference enable signal is output to sample -and hold unit 92
`on line
`95 when "line 10"
`in each vertical
`interval
`is detected
`
`representing the black "zero" level which is used as the DC reference
`level. The sample and hold unit then outputs a DC reference signal
`on line 93 to the data formatter so that the incoming data or text can
`be properly positioned relative to _"line 10" of the vertical
`interval.
`The properly formatted data is then output to video switches 98 to
`
`await transmission at the proper time in the vertical interval.
`
`When timing signal generator 94 reaches "line 17" in the vertical
`interval. a data enable signal" is output‘-on line 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 through on
`line 81 to the video scrambler unit B6. at the same time. a scramble
`disable timing signal is transmitted from data Iormatter 88 on 1ine'39
`to the scrambler controller 90 which in turn outputs a scramble disable
`
`This signal enables the data on line 81 to pass
`signal on line 3?.
`through the video scrambler and out on line 4-1 . without being
`
`scrambled. when timing signal generator detectsthe ‘end of "line I8“
`of the vertical interval, a data disable signal is directed via line 83 to
`the video switches 98 which turn off the data line. and turns on the
`
`is
`at the same time, a scramble enable timing signal
`video line.
`directed on line 89 to the scrambler controller which transmits a
`
`scramble enable signal to the video scrambler via line 3?. This signal
`enables video scrambler 86 so that the video signals coming in on line
`
`81 will be scrambled before being transmitted on line 44.
`It should also be noted that scrambler contr_oll'er unit 90 outputs
`
`a scramble/descramble timing signal on lineal to the data forniatter
`38. This signal is added to the data which is sent to video switches-98
`for transmission. This signal is utilized by the converter 40 as will be
`discussed later to control the descrarnbling of the video signal at the
`converter.
`I
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
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`15
`(cid:18)(cid:22)
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`20
`(cid:19)(cid:17)
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`25
`(cid:19)(cid:22)
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`30
`(cid:20)(cid:17)
`
`1as
`
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`
`TV,
`
`10
`
`10
`
`

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`ll
`
`Referring now to FIGURE 6, the addressableconverter unit 40
`of FIGURE 1
`is
`shown in greater detail.
`The converter, under
`
`control logic, processes the RF data—loaded
`direction of converter
`television signals from combined video output
`line 21 of head and
`signal combiner 29 and provi-desvidco and audio output fora television
`set. preferably on channels 3- or 4.
`In a two-way interactive system
`the RF input to the converter 40 also includes data from a two-way
`home terminal as will be shown and discussed in connection with
`
`-Figure 10. Both types of signals are input to an RFfdata separator 100'
`which directs the subscriber control "data to a converter control logic
`104 on SCB line 102. The RF data—loaded television signals are input
`to a conventional tuner 106 under the control of a tuner control unit
`
`103 which in turn receives instructions from converter control logic
`104.
`'
`
`Tuner 106 is preferably Nconventional unit using a sliding band‘
`pass filter and a band switched front end that is tuned with phase lock
`
`loop control. The RF output signals are detected by an IF/amp detector
`112 to provide a scrambled base-band video signal and a separate audio
`signal, Two-stage automatic gain control on feedback line llt} is provided
`to optimize noise reduction.
`
`A vertical interval data extractor H4 is connected to the scrambled.
`video output of unit 112 and provides a serial data stream extracted from
`the vertical
`interval of. the scrambled video signal
`to the converter
`control
`logic 104. A logic
`command signal
`for
`timing control
`is
`transmitted to extractor 114 by logic 104 on line 117.
`IF amp detector unit
`also generated a syncronizing signal
`from the video signatwtiich is
`transmitted to logic lD4 on line ll3.
`I
`A conventional video descrambler unit 116 processes the scrambled
`
`base-band video signal from the tuner and provides. a descrambled base
`band video signal which is directed to a textfgraphies generator 118. The
`scramblcfdescramblc timing signal generated by the scrambler controller
`an of HVP unit 52 and transmitted to converter 40 as part of the control
`_ data is processed lbv converter control logic 40 and input on line 101 to the
`video dcscrambler
`llfi
`to control
`is operation} The "channel
`sound
`
`information is amplitude adjusted or muted by an audio levelfmute control
`unit 120 controlled by a signal on data line 122 from logic N14.
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
`
`15
`(cid:18)(cid:22)
`
`20
`(cid:19)(cid:17)
`
`25
`(cid:19)(cid:22)
`
`30
`(cid:20)(cid:17)
`
`35
`(cid:20)(cid:22)
`
`wt!‘
`
`1'”!
`
`11
`
`11
`
`

`
`The textigrephics generator 130 provides display characters and
`graphic symbols that have been transmitted on the vertical interval. The
`converter control logic 104 directs screen control data on data link 124 to.
`
`a display memory 130 which in turn sends the formatted display characters
`along data link 132 to the textlgraphics generator 118 for display.
`The textfgraphics generator
`113
`includes a plurality of video
`switches which "are used to bypass the text/‘graphics generator with the
`
`channel video.‘ Optionally the video switches also permit the channel
`
`number display'to be superimposed on the video signallof the channel
`which is being presented. The outputof generator 118 is connected to a
`chanriel 3 or 4 modulator ‘L34 which in turn is connected to a subscriber's
`television set.
`
`is plugged into _a
`Preferably the subscriber's television set
`power control outlet on the addressable converter 40 which Is enabled
`on command from "a user keyboard unit 146 connected to converter
`control logic 104. All manual user inputs required by the system are
`preferably keyed in on keyboard I46. Alternately, the user may provide
`
`inputs from a remote control unit 1-lU_ having a keyboard similar to
`user keyboard 146.. Data is preferably sent from remote control unit
`14!} via an infra-red wireless link 142 to a conventional 1/R receiver 144
`
`which is connected to converter control logic 104. Hence, logic 104
`receives input data from the vertical interval data extractor 114 and
`from the subscriber via the keyboard 146 or the remote control unit
`
`is also received ‘from the
`in two-way cable systems input
`140.
`subscriber control bus 102. Converter control logic 104 processes this
`information -and operates the various modules in converter 40 under
`program control.
`"
`'
`Referring now to l’lGURE 7. converter control logic 104 is
`shown in greater detail. The central control logic N4 is ‘carried out
`by a microprocessor unit 410. Microprocessor 410 is preferably a single
`
`microprocessor chip containing a random access memory. a read-only
`memory and timer. Unit 410 interfaces between the tuner control
`circuit 108 of converter 40 and a two-way datallnk 412 connecting it
`to the rest of the converter control logic.
`A timer decoder unit 415 is connected to bus 412 and receives
`data from the vertical interval data extractor 114 on line 115. The V1
`data is buffered and decoded’ by unit
`414' preparatory to being
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
`
`(cid:18)(cid:22)
`15
`
`20
`(cid:19)(cid:17)
`
`(cid:19)(cid:22)
`25
`
`30
`(cid:20)(cid:17)
`
`35
`(cid:20)(cid:22)
`
`~.--
`
`‘,1
`
`.
`.
`+&-:——-u-¢m-.....1-*—
`
`.._._.—_....a——.....__.—.—.
`
`12
`
`

`
`I a
`
`-.v
`
`'-
`
`7
`
`ea;
`in addition. timer decoder unit 414
`transmitted to microprocesor 410.
`receives sync pulses from IF ampfdetector in on line 113. Unit 414
`
`includes line counting logic for determining when data is to be
`received on the vertical interval.
`'
`
`A subscriber control bus
`
`(SOB)
`
`interface unit 416 receives
`
`incoming. data from subscriber control bus 102 related to the functions
`01’ a two-way home terminal such as home terminal shown in FIGURE
`10. This SCB data is processed by interface unit 416 to be-trallsmitted
`
`_
`to microprocessor 4ltl.
`An identity ROM 428 is also connected by way of data link 412
`to microprocessor rill]. ROM «tin preferably contains a number of data
`codes which do not require changing in the normal operation of the
`
`system and which uniquely identify converter 40. These data codes
`include the identification number of
`the converter,
`the frequency
`configuration acceptable for the converter, and the "home channel"
`number,
`that is the channel number to which the converter will be
`tuned in the event of an emergency alert signal.
`
`Preferably units 410, _4l4, 416 and 4.20 are all conventional
`integrated circuit chips readily available in the marketplace. Suitable
`
`for microprocessor 41!] and timer decoder unit 414 are chip
`chips
`numbers 8045 and 8041 respectively. ' both manufactured by Intel
`Corporation. A suitable-chip for SCB interface unit 416 is UART chip
`6402 manufactured by Intersil Corporation. The identity ROM 420 is
`preferably a TI chip 74238, which is a 32 by 3 program read-only
`memory manufactured by Texas instruments.
`‘_
`.
`With reference now ‘to FIGURES 9 and 10, addressable converter
`
`In
`40 is shown in two different configurations for subscriber usage.
`FIGURE 9, addressable converter 4!]
`is connected in a stand alone,
`one-way configuration between a conventional RE’ splitter unit 150 and
`the subscriber's television set-46. This configuration is similar -to that
`shown in FIGURE 1. The RF signals from a cable TV plant 152 are
`transmitted by way ofa subscriber drop 154 to splitter 150 where they
`are separated and sent to a plurality of addressable converters such as
`unit 40. The remote control unit l40 for remote usage by a subscriber
`in controlling converter 40 is optional.
`
`In FIGURE 10. addressable converter 4!] is shown in an expanded
`
`In this
`system including a two-tray secu1'ity‘monitoring system 160.
`configuration, the RF signals from the CATV plant 152 are connected
`
`(cid:22)
`
`10
`(cid:18)(cid:17)
`
`15
`(cid:18)(cid:22)
`
`20
`(cid:19)(cid:17)
`
`25
`(cid:19)(cid:22)
`
`30
`(cid:20)(cid:17)
`
`35
`(cid:20)(cid:22)
`
`‘her-‘
`
`"‘r"§“V
`
`13
`
`13
`
`

`
`-
`
`_
`
`-
`
`'
`
`.* 75
`=55.‘
`
`by way of "a subscriber drop 154 to a two-way home terminal unit 34
`which permits various accessor-devices such as security monitoring
`system 160 to be controlled by a separate conventional
`two-way
`interactive data communications system (not shown) using cable plant
`152.
`The converter 40 is connected to hometerminal 34 by a
`
`SCB bus 162
`subscriber control bus ($03) 162 via SCB adapterkfifi.
`connects to the internal ISCB bus 102 of converts 40 as shown in Figure
`6. The SCB bus 152 preferably carries downstream RF cable television
`signals and two-way data signals over a single‘c'oaxial.cab1e link 162
`connected to the addressable converter '40. Additional converters may
`be connected by way of a two or four-way splitter 164 that has been
`modified to pass DC signals.
`
`I In this expanded configuration. addrefiable converter unit 40 is
`enabled to "talk back"
`to the
`two-way interactive data com-
`
`munications system by way of the subscriber control bus adapter 156
`and the two-way home terminal 34. The two-way ‘home terminal 3-:
`
`-
`
`is also connected to the se