an
`
`XR
`
`495069387
`
`'
`
`Exhibit 12 12
`
`United States Patent
`
`[19]
`
`Walter
`
`[11] Patent Number:
`
`4,506,387
`
`[45] Date of Patent:
`
`Mar. 19, 1985
`
`Primary Examiner——Robert L. Griffin
`Assistant Examiner——Timothy K. Greer
`Attorney, Agent, or Firm——Albert L. Jeffers; Anthony
`Niewyk
`
`[57]
`
`ABSTRACI‘
`
`A programming-on-demand cable system is provided
`which allows any one of a plurality of individual users
`to request anyone of a plurality of video programs they
`wish to view from a library of programs, and permits
`the requested program to be available for viewing on a
`conventional television set at the user’s location follow-
`ing a request initiated by the user. Each program is
`preprogrammed in a memory device selectable by a
`host computer at a central data station in response to an
`address signal transmitted from the user. The host com-
`puter in conjunction with other electronics transmits
`the video program at a high non-real-time rate over a
`fiber optic line network to a data receiving station at the
`user’s location. The data receiving§tation then converts
`the received optical data back to electrical data and
`stores it for subsequent rea1~time transmission to the
`user’s television set. The system permits the user to
`view any one of a number of programs transmitted on a
`non-real—time basis, and also allows the user to store the
`transmitted program at his data receiving station for an
`indefinite period of time for viewing at a later date. A
`method is also provided for transmitting the programs
`on a non-real—time basis.
`
`14 Claims, 4 Drawing Figures
`
`[54] PROGRAMMING-ON-DEMAND CABLE
`SYSTEM AND METHOD
`
`[76]
`
`Inventor:
`
`Howard F. Walter, P.O. Box 11617,
`Fort Wayne, Ind. 46859
`
`[21] Appl. No.: 497,885
`
`[22] Filed:
`
`May 25, 1983
`
`Int. Cl.3 ............................................. .. H04N 7/16
`[51]
`[52] U.S. Cl. ...................................... .. 455/612; 455/3;
`455/6; 455/53; 358/86; 370/3
`[58] Field of Search ................... .. 455/4, 5, 6, 53, 612;
`358/86, 102, 114
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`.................... .. 340/717
`3,696,392 10/1972 Fossum et al.
`3,725,874 4/1973 Van Heel . .. .. ...
`. .. .. 364/200
`3,931,512
`1/1976 Kent et al.
`.. .. ..
`.. ... 250/205
`3,997,913 12/1976 Rittenbach .. ....
`. .. .. 360/8
`4,062,043 12/1977 Zeidler et al.
`. .... .
`.. ..... 358/86
`4,071,697
`1/1978 Bushnell et a1.
`.. 179/2 TV
`4,131,765 12/1978 Kahn ...............
`179/81 R
`4,135,202
`1/1979 Cutler . . . .. .
`.. .. ... 358/86
`4,381,522 4/1983 Lambert ................................ 358/86
`
`
`
`OTHER PUBLICATIONS
`
`16 Shows & What Do You Get from Video Magazine,
`Jul. 1983.
`
`Dr. M. Kawahata, “The HI—OVIS Optical Communi-
`cation System”, (17-20 Sep. 1979).
`-
`
`MEMORY MODULES
`
`SWITCHING
`SYSTEM
`
`
`
`
`CDMMHNICATIONS
`CONTROLLER
`
`LASER DIODE
`MODULES
`
`
`
`PHOTODIODE
`MODULES
`
`11
`
`. ......._..« \
`Page 00001
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`Page 00001
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`

`
`U.S. Patent Mar. 19,1985
`
`Sheetl of3
`
`4,506,387
`
`‘)2
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`
`I I
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`Page 00002
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`Page 00002
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`

`
`U.S. Patent Mar. 19,1985
`
`Sheet2of3
`
`4,506,387
`
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`Page 00003
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`Page 00003
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`

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`U.S. Patent Mar. 19,1985
`
`Sheet3of3
`
` 4,506,387
`
`I98
`
`F i E,
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`
`INTERFERENCE
`
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`Page 00004
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`Page 00004
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`

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`1
`
`4,506,387
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`PROGRAMMING-ON-DEMAND CABLE SYSTEM
`AND METHOD
`
`BACKGROUND OF THE INVENTION
`
`This invention pertains to a broadcasting cable sys-
`tem, and more particularly to a programming-on-
`demand cable system wherein any one of a plurality of
`stored video programs can be broadcast in a non-real-
`time basis to a user.
`Generally and to the best of applicant’s knowledge,
`existing video broadcast services provide a user any one
`of a plurality of programs to be viewed on a real-time
`basis. The user may select any one of the video pro-
`grams, however, he is restricted in his enjoyment of the
`program in that the user has no control over when in
`time the program is broadcast to his video or television
`set. For example, video programs are routinely an-
`nounced in video or television guides listing the pro-
`grams available to the user for his choice in viewing at
`a specific time of day. Consequently, the user does not
`have the choice of viewing the program when he so
`desires, but rather is restricted to that particular time
`listed in the video or television guide.
`Moreover,
`it would be much too impractical and
`costly to provide the necessary equipment to process
`numerous concurrent requests for real-time transmis-
`sion of video programs at any time desired by the users.
`Present broadcasting systems transmit the data by
`one of many methods, for example, “over-the-air”, elec-
`trical lines or cables, fiber optic lines or cables, and the
`like. Presently, transmission by means of fiber optics is
`becoming more practical, however, the user is still re-
`stricted to viewing his program at a broadcasting time
`not of his choosing.
`SUMMARY OF THE INVENTION
`
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`The present invention overcomes the problems and
`disadvantages of present broadcasting systems by pro-
`viding an improved programing-on-demand cable sys-
`tem.
`The programming-on-demand cable system of the
`present invention overcomes the inability of a user to
`select any one of a number of video programs for view-
`ing at a time of his choice by providing a non-real-time
`transmission of the desired program. Any number of
`various programs are stored in memory devices at a
`central location or library and are viewable by a user at
`any time by means of the cable system of the present
`invention. A host computer at the library is electrically
`connected to the memory devices, and upon receiving
`an address signal from a keyboard located at the user’s
`location, the host computer selects the memory device
`identified by the address signal, and causes the program
`stored therein to be transmitted by a fiber optic line to
`a data receiving station at the user’s location. A central
`data station, of which the host computer is a part, causes
`the program identified by the address signal to be con-
`verted from electrical data to optical data and transmit-
`ted over the fiber optic line to the data receiving station,
`which then reconverts the optical data back to the origi-
`nal electrical data. Thereafter, the reconverted electri-
`cal data is transmitted to the user’s television set for
`virtually immediate viewing; or the reconverted electri-
`cal data is stored in a memory module in the data receiv-
`ing station for subsequent viewing by the user at the
`time of his choice. If necessary, the electrical data re-
`ceived by the data receiving station is reconstructed,
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`which may be necessary if the electrical data is received
`in a form not acceptable by the television for viewing,
`and is transmitted at a normal rate to the user’s televi-
`sion.
`Further, the data transmitted from the central data
`station to the data receiving station is transmitted in
`multiplexed fashion so that the equipment at the central
`data station is dedicated for only a short period of time,
`for example, on the order of 20 to 30 seconds, thereby
`minimizing any delay between transmission of an ad-
`dress signal by the user and the receipt of the desired
`program at the user’s location.
`To facilitate the storage and manipulation of the
`video programs, and to allow the method to be placed
`under automatic computer control, the electrical data
`representing each video program is converted to com-
`pressed digital form and stored in suitable high density
`memory devices.
`'
`In one form .of the invention, there is provided an
`improvement in a broadcasting system including a cen-
`tral data station having means for converting electrical
`data to optical data, a data receiving station having
`means for reconverting the optical data back to the
`electrical data, a fiber optic line means connecting the
`central data station and data receiving station for trans-
`mitting the optical data therethrough, and a broadcast-
`ing device electrically connected to the receiving sta-
`tion for receiving and broadcasting the reconverted
`electrical data to the user. The improvement comprises
`a plurality of memory devices electrically connected to
`the central data station, wherein each memory device is
`identifiable by a respective address signal and has pre-
`programmed therein respective electrical data repre-
`senting a video program. Each memory device is re-
`sponsive to its received address signal to thereby trans-
`mit its electrical data to the converting means. A user-
`operable generator device at the user’s location is oper-
`atively connected to the central data station for selec-
`tively generating any one of the address signals and
`transmitting a selected address signal to the central data
`station, whereby the central data station transmits that
`address signal to the identified memory device which
`then transmits its electrical data to the -converting
`means for subsequent transmission to and broadcasting
`by the broadcasting device at the user’s location.
`The present invention also provides a method for
`broadcasting on a non-real-time basis any one of a plu-
`rality of electrical data representing different video
`programs comprising the steps of providing a central
`data station including an electro-optical transducer for
`converting electrical data to optical data, a data receiv-
`ing station including an opticoelectrical transducer for
`reconverting the optical data back to the electrical data,
`a fiber optic line means connecting the transducers, and
`a broadcasting device electrically connected to the data
`receiving station for receiving and broadcasting the
`electrical data transmitted. The method further com-
`prises the steps of providing a plurality of memory
`devices electrically connected to the central data sta-
`tion, wherein each of the memory devices is identifiable
`by a respective address signal, and preprogramming
`each memory device with respective electrical data
`representing a video or broadcast program, each mem-
`ory device being responsive to its received address
`signal to thereby transmit its electrical data to the elec-
`tro-optical transducer. Further provided is a user-oper-
`able generator device at the location of the broadcasting
`
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`-
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`device and which is operatively connected to the cen-
`tral data station and responsive to input applied by the
`user for generating any one of the address signals. Fur-
`ther steps are applying an input to the generator device
`to generate a selected one of the address signals, and
`transmitting the generated address signal to the central
`data station for identification of the memory device
`identifiable by the generated address signal. Thereafter,
`transmitting the generated address signal to the identi-
`fied memory device, whereby the memory device trans-
`mits its electrical data to the electro-optical transducer
`for converting the electrical data to optical data and
`transmitting the optical data through the fiber optic line
`to the opticoelectrical transducer for reconverting the
`optical data back to the electrical data, and then trans-
`mitting the electrical data to the broadcasting device for
`the broadcast thereofi
`It is an object of the present invention to provide a
`programming-on-demand cable system which permits a
`user to selectively control which program he desires to
`view at a particular time, subject only to the contents of
`the library of video programs maintained at the central
`data station.
`
`Another object of the present invention is to provide
`a method for allowing a user to selectively control
`when and what program he desires to view‘, subject
`only to the contents of the library of video programs
`available.
`
`Further objects of the present invention will appear
`as the description proceeds.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above mentioned and other features and objects
`of this invention, and the manner of attaining them, will
`become more apparent and the invention itself will be
`better understood by reference to the following descrip-
`tion of an embodiment of the invention taken in con-
`junction with the accompanying drawings, wherein:
`~
`FIG. 1 is a schematic of a preferred embodiment of
`the present invention;
`FIG. 2 is a schematic of a portion of the central data
`station and a multi-fiber data bus of the embodiment in
`FIG. 1;
`FIG. 3 is a schematic illustrating how data is divided
`among a memory device of the embodiment in FIG. 1;
`and
`
`FIG. 4 is a schematic illustrating a portion of the
`multifiber data bus and the data receiving station of the
`embodiment of FIG. 1
`
`DESCRIPTION OF A PREFERRED
`EMBODIMENT
`
`Referring to FIG. 1, programming-on-demand cable
`system 10 is schematically illustrated generally compris-
`ing central data station 12, data receiving station 14, a
`multi-fiber data bus 16, and keyboard 18.
`Central data station 12 includes host computer 20
`electrically connected to electronic switching system
`.22. The electronic switching system 22 is electrically
`connected to a library of memory modules 24, 26, 28,
`30, 32, 34,.as indicated by digital data flow arrows 36,
`38, 40, 42, 44, 46, respectively. Electronic switching
`system 22 selectively connects any one of the memory
`modules 24-34 to multi-fiber data bus 16, as will be
`described in detail hereinafter. Although only one data
`bus 16 is illustrated in FIG. 1, the present invention
`contemplates numerous such data buses 16 wherein
`electronic switching system 22_ is capable of selectively
`
`4
`electrically connecting any memory module 24-34 to
`any one or plurality of other such data buses 16.
`Although only six memory modules 24-34 are illus-
`trated in FIG. 1 as representing a library of video pro-
`grams, it should be understood that more or fewer such
`memory modules may be included in the library and
`connected to electronic switching system 22. In this
`particular embodiment, only six such memory modules
`24-34 are illustrated, and each one contains a specific
`video program for broadcasting. The video programs
`are preprogrammed into respective memory modules
`24-34 in digital format for rapid and inexpensive trans-
`mission, as will be described in greater detail below. It
`should be realized however, that the video programs
`may be stored in other formats, such as an analog for-
`mat.
`Central data station 12 further includes four laser
`diode modules 48, 50, 52, 54, each of which includes
`four pulse code modulators respectively connected in
`series with four laser diodes for converting digital data
`to optical data and one holographic plate, a description
`of which will be made in greater detail below with
`reference to FIG. 2. Continuing with FIG. 1,
`laser
`diode modules 48-54 are optically connected to fiber
`optic .lines 56, 58, 60, 62, respectively, of multi-fiber data
`bus 16.
`
`Host computer 20 is also electrically connected to
`communications controller 64 by line 66, which is fur-
`ther electrically connected to respective laser diode
`modules 48-54 by lines 68, 70, 72, 74. Following a com-
`mand from host computer 20, communications control-
`ler 64 assumes control of fiber optic lines 56-62 of data
`bus 16.
`
`Host computer 20 is electrically connected to elec-
`tronic switching system 22 by line 76, and electronic
`switching system 22 is electrically connected to laser
`diode modules 48-54 as illustrated by digital data flow
`arrows 78, 80, 82, 84, respectively.
`Continuing to refer to FIG. 1, data receiving station
`14 includes four photo-diode modules 86, 88, 90, 92
`optically connected to fiber optic lines 62, 60, 58, 56, by
`fiber optic lines 94, 96, 98, 100, respectively. It is empha-
`sized that fiber optic lines 56-62, which make up four of
`the five lines in multi-fiber data bus 16, continue on as
`illustrated in FIG. 1 by arrows to additional users. Each
`photodiode module 86-92 includes four filters, four
`photodiodes, and four demodulators connected in series
`as illustrated in FIG. 4, a more detailed description of
`which will continue below.
`Photodiode modules 86-92 are connected to memory
`module 102 as illustrated by digital data flow arrows
`104, 106, 108, 110, respectively. Data receiving station
`14 further includes control computer 112 electrically
`connected to memory module 102 by line 114, to DA
`(digital-to-analog) converter 116 by line 118, and to RF
`modulator 120 by line 122. Control computer 112 is
`electrically connected to each of the photodiode mod-
`. ules 86, 88, 90, 92 by lines 117, 119, 121, 123, respec-
`tively, which branch off from line 115; this allows con-
`trol computer 112 to transmit clock signals for data that
`requires synchronization to modules 86-92.
`Host computer 20 is connected to control computer
`112 by line 124, laser diode module 126, fiber optic line
`128, fiber optic line 129 coupled to line 128, photodiode
`module 130, and digital data flow arrow 132. Laser
`diode module 126 includes only two pulse code modula-
`tors, two laser diodes, and one holographic plate; and
`photodiode module 130‘inc1udes two interference fil-
`
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`4,506,387
`
`5
`ters, two photodiodes, and two demodulators, which
`will be described in greater detail below with reference
`to FIG. 2. Fiber optic line 128 is the fifth of the five
`fiber optic lines in data bus 16 and continues on as illus-
`trated in FIG. 1 to additional users. Communications
`controller 64 is connected to control computer 112 by
`line 131, laser diode module 126, fiber optic lines 128,
`129, photodiode module 130, and digital data flow
`arrow 132.
`
`Data receiving station 14 further includes automatic
`modem 134 electrically connected to control computer
`112 by line 136. Automatic modem 134 communicates
`with host computer 20 by means of line 138, which is
`connected to the user’s telephone line 140, telephone
`line 142, modem 143, and line 145.
`Keyboard 18 is electrically connected to control
`computer 112 by line 144, and television 146 is con-
`nected 'to RF modulator 120 by analog data flow arrow
`148.
`
`Referring now to FIG. 2, a more detailed description
`of the interface between central data station 12 and
`multi-fiber data bus 16 will be made. FIG. 2 illustrates in
`an exploded manner the method in which laser diode
`modules 48-54 are operatively connected to fiber optic
`lines 56-62, respectively, and since the connection be-
`tween each of the four laser diode modules to its respec-
`tive fiber optic line is identical only one such descrip-
`tion will be made and will suffice for all four.
`Briefly, each program in each digital memory module
`24-34 is logically divided into 16 data cells in that par-
`ticular memory module so as to reduce the transmission
`time of the program. Each laser diode module 48-54 is
`designed to transmit four of the sixteen cells of data
`representing the program and are illustrated in FIG. 2
`by digital, data flow arrows 150, 152, 154, 156, which
`are included in, by example only in FIG. 1, digital data
`flow arrow 46 and make up the digital data flow arrow
`84 when memory module 34 is selected.
`It should be understood that, while four groups of
`data streams 150-156 are shown in FIG. 2, the data
`included in these groups of data streams is not identical.
`Each of the sixteen illustrated data streams 150-156
`transfers data from respective ones of the sixteen unique
`data cells of one of the memory modules 24-34, each
`data stream comprising a portion of a single program.
`Continuing to refer to FIG. 2, four of the sixteen cells of
`data representing a single program of memory module
`34 are separately transmitted to pulse code modulators
`158, 160, 162, 164 for subsequent transmission to laser
`diodes 166, 168, 170, 172, respectively. Pulse code mod-
`ulators 158-164 are electrically connected to laser di-
`odes 166-172 by lines 174, 176, 178, 180, respectively.
`Digital data transmitted to pulse code modulators
`158-164 are individually modulated and transmitted to
`laser diodes 166-172 by lines 174-180, and laser diodes
`166-172 then transmit the digital data as optical data
`having different light wavelengths to holographic plate
`182. As illustrated laser diodes 166-172 are oriented
`such that the four different light wavelengths L1, L2,
`L3, L4, converge at holographic plate 182, which redi-
`rects the four wavelengths in a parallel manner to fiber
`optic line 62. As described, the digital data transmitted
`to laser diode module 54 is now spectrally multiplexed
`in fiber optic line 62. Various methods for deflecting
`light beams, for example, by holographic plates, are
`disclosed in U.S. Pat. No. 4,062,043 issued Dec. 6, 1977
`to Zeidler et al. The methods disclosed in Zeidler are
`
`6
`used to deflect multiple light wavelengths onto a single
`fiber.
`In a similar manner the other twelve cells of digital
`data are likewise spectrally multiplexed and transmitted
`through fiber optic lines 56-60.
`FIG. 2 further illustrates the interface between fiber
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`optic line 128 with central data station 12 and multi-
`fiber data bus 16 by means of laser diode module 126
`comprising pulse code modulator 184 electrically con-
`nected in series with laser diode 186 and pulse code
`modulator 188 electrically connected in series with
`laser diode 190. Digital data flow arrow 193 represents
`line 124 connecting host computer 20 to laser diode
`module 126 in FIG. 1. Digital data flow arrow 193
`transmits certain control data from host computer 20 to
`data receiving station 14 for display on the user’s televi-
`sion 146. Digital data flow arrows 192, 194 represent
`line 131 (FIG. 1) connecting communications controller
`64 to laser diode module 126. Flow arrow 192 transmits
`other control data to control computer 112, and flow
`arrow 194 illustrates transmission of synchronization
`data from communications controller 64 to control
`computer 112. The control and synchronization data
`are spectrally multiplexed in fiber optic line 128 in an
`identical manner as described above for line 62.
`As explained above, optical data transmitted from
`laser diodes 166-172 is oriented to converge on holo-
`graphic plate 182, however, it is recognized that the
`optical data could be transmitted from laser diodes
`166-172 in a parallel fashion to a convex lens to be
`deflected to holographic plate 182.
`Referring now to FIG. 3, an exemplary description
`will be made of how digital data is stored in one of the
`memory modules 24-34. FIG. 3 illustrates a memory
`module 196'containing only three cells 198, 200, 202 in
`this example. Memory module 196 is of the recirculat-
`ing shift register type, and is logically divided into the
`three cells 198-202 and is illustrated as storing a nine bit
`program. Storing is by the bit rotation logic method
`wherein bit one is stored in cell 202, bit 2 stored in 200,
`bit 3 stored in cell 198, bit 4 stored in cell 202, etc. The
`data are retrieved from memory module 196 in a paral-
`lel fashion and are subsequently transmitted to the fiber
`optic lines of the data bus, which also operate in paral-
`lel. The purpose for the use of bit rotation is to permit
`memory module 102 in FIG. 1 in data receiving station
`14 to operate at a lower data rate during playback.
`Referring now to FIG. 4, there is schematically illus-
`trated the interface between fiber optic lines 94-100 and
`129 at data receiving station 14. Since the interface
`between fiber optic lines 94-100 are identical, and 129
`similar, only one such interface will be described using
`fiber optic line 94. Fiber optic line 94 is connected to
`photodiode module 86 comprising diverging optical
`element 204, interference filters 206, 208, 210, 212, pho-
`todiodes 214, 216, 218, 220, and demodulators 222, 224,
`226, 228. Photodiodes 214-220 are connected to respec-
`tive demodulators 222-228 by respective lines 230, 232,
`234, 236. The spectrally multiplexed light beam is trans-
`mitted from fiber optic line 94 to diverging optical ele-
`ment 204 which divergingly transmits the light beam to
`interference filters 206-212, each of which permits only
`a discrete wavelength to pass therethrough to thereby
`demultiplex the light beam. As illustrated in FIG. 4,
`filter 206 permits only wavelength L1 to pass through,
`filter 208 permits only wavelength L2, filter 210 permits
`only wavelength L3, and filter 212 permits only wave-
`length L4 to pass through. The operation of diverging
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`optical element 204 is known and disclosed in U.S. Pat.
`No 4,062,043 issued Dec. 6, 1977 to Zeidler et al., which
`is incorporated by reference herein.
`The light wavelengths are then transmitted to photo-
`diodes 214-220 and demodulators 222-228 for convert-
`ing the optical data back to the original digital data The
`data is then transmitted to memory module 102 as illus-
`trated by digital data flow arrow 104 in FIG. 1. Mem-
`ory module 102 is arranged identically to memory mod-
`ules 24-34 with sixteen parallel cells for containing the
`data.
`
`8
`selects the one identified memory module 24-34 con-
`taining the selected video program. Following this, host
`computer 20 signals communications controller 64 to
`assume control of laser diode modules 48-54, 126, after
`which communications controller 64 causes electronic
`switching system 22 to transmit the selected digital data
`to laser diode modules 48-54 and thereafter to data
`receiving station 14 as described above. Communica-
`tions controller 64 communicates with control com-
`puter 112, as described above, when each step of the
`transmission sequence is begun and terminated.
`After transmission, the video program is stored in
`memory module 102 of data receiving station 14 as
`earlier described, and communications controller 64
`communicates with host computer 20 that data trans-
`mission is complete. Host computer 20 then informs the
`user via digital data flow arrow 193 (FIG. 2) that the
`program is ready for viewing by displaying a ready
`signal on television 146. The user begins the video pro-
`gram by depressing a “START” switch on keyboard
`18, whereby control computer 112 signals _memory
`module 102 to transfer the digital data to DA converter
`116 as illustrated by digital data flow arrow 238 for
`converting the digital data to analog data upon com-
`mand from control computer 112. Thereafter control
`computer 112-commands converter 116 to transmit the
`analog data to modulator 120 as illustrated by digital
`data flow arrow 240, and then to television 146 via the
`analog data flow arrow 148.
`Although the above description includes converting
`the digital data to analog data at the data receiving
`station 14 for display on television 146, it is contem-
`plated that this step may be eliminated with television
`sets capable of receiving digital data for display thereof.
`Although the above description was made in terms of
`a fully completed transmission of a programbefore
`viewing by the user, the present invention fully contem-
`plates that the user may begin viewing his program
`before the complete transmission thereof. Central data
`station 12 may transmit only a portion of the selected
`program to the user for his viewing, and then begin
`transmitting a portion of another selected program to a
`second user. This permits central data station 12 to
`simultaneously handle several users, rather than waiting
`for complete transmission of one selected program be-
`fore proceeding with another user’s address signal.
`While this invention has been described as having a
`preferred embodiment, it will be understood that it is
`capable of further modifications. This application is
`therefore intended to cover any variations, uses, or
`adaptations of the invention following the general prin-
`ciples thereof, and including such departures from the
`present disclosure as come within known or customary
`practice in the art to which this invention pertains and
`fall within the limits of the appended claims.
`What is claimed is:
`1. In a broadcasting system including a central data
`station, a data receiving station, a fiber optic line means
`connecting said central data station and said data re-
`ceiving station, said central data station including means
`for converting electrical data to optical data and trans-
`mitting said optical data through said fiber optic line
`means to said data receiving station, said data receiving
`station including means for reconverting said optical
`data back to said electrical data, and a broadcasting
`means electrically connected to said data receiving
`station for receiving and broadcasting said electrical
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`Thereafter the digital data is retrieved and fed to the
`DA converter 116 on command from control computer
`112 for converting the digital data to analog data, and is
`then transmitted to RF modulator 120 for subsequent
`transmission and broadcasting by television 146.
`The data in memory modules 24-34 is in compressed
`digital form, thereby accomplishing a considerable sav-
`ings in transmission costs. After host computer 20 has
`signaled electronic switching system 22 to electrically
`connect the selected one of the memory modules 24-34,
`host computer 20 then signals communications control-
`ler 64 to assume control of the compressed digital data
`transmitted to laser diode modules 48-54. Communica-
`tions controller 64 also then assumes control of laser
`diode module 126. The digital data is compressed in
`memory modules 24-34 by a technique known as inter-
`frame differential pulse code modulation. The digital
`data is received, as described above, at data receiving
`station 14 and reconstructed by control computer 112.
`The inter-frame differential pulse code modulation
`technique just described is known in the art, and addi-
`tional circuitry may be added to avoid problems caused
`by rapid motion in the picture. Further, the bit rate
`requirements may be reduced even further by means of 35
`other similar but more complicated procedures.
`By utilizing inter-frame differential pulse code modu-
`lation, each second of video program playing time
`yields about 44 megabits. Further, according to the
`present state of the art, 650 megabits per second can be
`transmitted on a single wavelength, and since in the
`present embodiment there are 16 optical data channels
`in the four fiber optic lines 56, S8, 60, 62, the total trans-
`mission rate is 10,400 megabits per second. Therefore, a
`two hour movie can be transmitted in about 31 seconds
`(7,200 seconds><44 megabits per second / 10,400 mega-
`bits per second).
`In operation, the user determines which program he
`desires to watch, and then inputs the correct address
`signal
`in keyboard 18 which transmits the signal to
`computer control 112, which in turn transmits the signal
`to automatic modem 134. Automatic modem 134 then
`transmits via lines 138, 142, modern 143, and line 145 the
`address signal to host computer 20 which determines
`which data bus 16 serves the user and enters the address
`signal in a queue for the particular data bus 16 of the
`user. Host computer 20 then transmits a receipt signal
`through line 145, modem 143, lines 142, 138, automatic
`modem 134, and line 136 to control computer 112,
`which in turn transmits the signal through line 122 to
`RF modulator 120 for display on television 146, thereby
`indicating to the viewer that the host computer 20 has
`received and entered the selected address signal. There-
`after, host computer 20 transmits other instructions and
`information to the viewer via digital data flow arrow
`193 (FIG. 2) which represents line 124 in FIG. 1. When
`the user’s turn comes up, host computer 20 transmits the
`address signal to electronic switching system 22 which
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`data transmitted from said data receiving station, the
`improvement comprising:
`V
`a plurality of memory devices electrically connected
`to said central data station, each memory device
`being identifiable by a respective address signal and
`having a plurality of datacells, each d