CA1155952A - Subscriber-limited reception television broadcast security encoder-decoder system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method and apparatus for encoding and decoding of standard television signals are disclosed for enabling reception thereof in an intelligible manner only by authorized subscribers. The scrambling of the audio signals is effected by conversion of analog audio signals to coded digital audio signals. There is provided a subscription television transmitter which can transmit separately a plurality of unique pulse coded control signals consisting of 32-bit binary pulse trains to identify individual authorized sub-scribers and to provide information needed to unscramble the scrambled video and audio signals. The transmitter generates television signals having a program video portion and a program aural portion in a non-standard format to enable reception of both program video and program audio portions in an intelligible manner only by authorized sub-scribers. It includes: an encryption code signal generating means; a carrier signal generating means; means for digitizing the program audio signal; means responsive to the encryption code signal for digitally encrypting the digitized program audio signal from the digitizing means; and means for com-bining the encryption codes signal, the digitized and encrypted audio program signal and a video program signal, with the carrier signals whereby the encryption codes signal, the digitized and encrypted audio signal and the video signal can be individually separated at a receiver.

Description

9 ~j 2 BACKGROUND OF THE INVENTION

This invention relates generally to security or subscription television systems and more particularly, it relates .to a method and system for encoding and decoding of standard television signals thereby-enabling reception ;
thereof in an intelligible manner only by authorized .subscribers.
Generally, there are known in the prior art various types o~ secure subscription television sytems in which televisio~ signals are transmitted in a coded form for use only in subscribers' receivers having proper decod-ing means. In these systems,.the coding is accomplished by modifying th~ sound and/or video portions of the television siynals rendering them uninte71igi~1e or unpleasant to non-subscribers or to subscribers who had not paid a fee to .
the broadcaster.
. In these proposed secure subscription television sys~ems, upon decodi.n~ the modified television signals, it was generally required that the precisQ modific2tion signals . must be removed or any missing signals must be sener~ted and added to the modified television signals to D~oduce a restored.video as similar as possible to it~ original ~uality. .
Problems existed in these techniques due to the facL tha~
the quality of the picture was generally 5ubjec~ to d~gradation ar~d/or that dificulties were encountered in maintaining criti-cal phase and other signal relationships in restoration, 9 ~ ~
The efectiveness of the secure subscription television systems is measured.by the degree of success which it has in deterring unauthorized viewers frcm watching the modified television signals transmitted and in preventing the duplication o the decoding means.
: Ithas also been experienced that in general the decoding technique utillzed in the prior art systems CQUld be easily duplicated by many resourceful viewers.and thus defeat the security thereof. It would,. therefore~ be desirable to provide.a method and sys~em for encoding and . decoding television signals in which maximum security is achieved and which will effectively deter u~authorized viewers in attempting to defeat the security. Moreover, it is needed to provide a system such that the theft ., .15 thereof will be of little use or value.
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: . In addition, the prior secure subscription . , .
television systems have a d.isadvantage in that none of them possess a positive and coni:inuous control means for.
~ controlling automatically ~he decoder at the v.~xious sub-- 20 scriber stations whereby any or all of the decod2Ls become `selectively disabled or "locked out" if it does no~ receive , , .
~`; the appropriate control signals from the broadcaster period-ically before a pre-determined interval of time.has elapsedO
Thus, it would be desirable to provide a method and system for encodïng and decoding of standard television signals in 9 ~ 2 which the decoder at the subscriber's station are de?endent c~ntinuously upon control signals transmitted by the broad caster. In the absence of the periodic control sign21s, the decoder will automatically and rapidly become disabled . rendering it essentially useless withou~ the necessity o. .
.- physically traveling to the subscriber's location.
It would also be suitable to provide in connection with a subscription television system means by which the subscribers could select the programs desired in a short time in advance of ~elecasting in a simple and easy ~anner.
To this end, telephone communication circuitry can be provided so.that the ~ubscribers can request their programs to the broadcaster via a telephone interface which will transmit the subscriber's request to the broadca5ter autom~-~ 15 tically wit~out any great effort on his part o~her than by : simply depressing a button at the subscriber's siteO The . ' telephone interface would automatically dial the broadcaster'stelephone number, transmit ~he subscriber's ~nique account code to a computer at the broadcaster's site, and thus make-possible ~he program selection by the subscriber at æ~y time prior to the broadcast~ Further, this would allow .he s~ tem to be very reliable and substantially maint~enance-l_ee 2~ter the initial installation since all ~he control signals are done via over-the-air transmission and requests for ser~ice are done electrically on the tel~hone interface. ~here is eliminated the need to physically travel to the su~scriber~s location during normal use so as to supply or retriev~ coin.s~
cards, or tapes and the li~e for billing purposes as encountered in some prior art systems.

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SUMMARY_ OF THE INVENTION

Accordingly, it i~ an over-all objective of the present invention to provide a new and novel method and apparatus for encoding and decoding standard television signals which possess very high security and deter un-authorized viewers.
Another object of this invention is-to provide an improved television transmitter for encoding standard television signals which restores the scrambled video and audio signals withou~ degradation in picture and sound qualities.
Still another object of this invention is to pro-vide a television transmitter for encoding standard television signals wherein a plurality of unique pulse-coded control signals consisting of 32-bit binary pulse trains are transmitted separately to identify individual authorized subscribers and to provide the information needed for unscrambling of the ~ideo and audio signals in the same s,equence as used for scxambling.
Still another object o* this invention is to provide a television transmitter for encoding standard tele-vision signals wherein the audio scrambling lS accomplished by conversion of analog audio signals to coded digital audio signals.
Still another object of this invention is to provide a television transmitter for encoding standard television signals wherein control means continuously enable decoding means at the various subscriber stations whereby any or all of the decoder means become selectively disabled or "locked out" if it does not receive the appropriate control signals .

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from the broadcaster perlodically before a pre-determined interval of time has elapsed.
Yet still another object of this invention is to provide a television transmitter for encoding standard television signals wherein telephone communication circuitry allows the subscribers to request their programs to the broadcaster via a telephone interface.
Yet still another object of this invention is to provide a television transmitter for encoding standard television signals having means for transmitting aural barker signals simultaneously with scrambled video signals and means for receiving the barker signals regardless of whether the subscriber is authorized to receive the un-scrambled video signals so as to promote usage of the sub-scription television system.
In accordance with the present invention, there is provided a subscription television transmitter for generating television signals having a pxogram video portion and a program aural portion in a non-standard format to enable reception of both program video and prcgram portions in an intelligible manner only by authorized subscribers; said television transmitter comprising:
a) encryption code signals generating means î
b) at least one carrier signal generator means adapted to convey by cable or over-the-air transmission the program video and program aural portions and the encryption codes signal from the transmitter to authorized subscribers;
c) means for digitizing the program audio signal;

' 1 ~5952 d) means responsive to the encryption code signal for e~crypting the digitized program audio signal from the digitizing means;
e) means for combining ~he encryption codes signal, ~he digitized and encrypted audio program signal and a ~ideo program signal, with the carrier signals whereby the encryption codes signal/ the digitized and encrypted audio signal and the video signal can be individually separated at a receiver.
Briefly, the presen~ invention provides a method and system for encoding and decoding of standard television signals thereby enahling reception thereof in an intelligibla manner only by authorîzed subscribers. The audio scrambling is accomplish~d by conversion of analog audio signals to coded digital audio signals. A plural.ity of unique pulse-coded control signals consisting of 32-bit binary pulse trains are transmitted separately to identify individual authorized subscribers and to provida the information needed to unscramble the scrambled audio and video signals. When there is a comparison b~tween one of t:he pulse-coded control signals wi~h a unique address code associated with a particular subscriber, unscrambling of the video and auaiol~ ~ -~~~-~`~~ - ~ ~~~~
... .. _ ___ ... . , . .... __ . . _ . _~ ~ .

signals occurs in the same sequence as used for scrambling to provide restored video and audio signals wi~hou~ degrada~
tion in picture and sound,qualities. This scra~bling technique is done without affecting or altering the normal specification for composite video, color and aural transmission or'for the broadcaster's transmitter utilized in the normal telecasting.
It will be a~preciated from the foregoing that .
the present invention provides a new and novel method and ... .
; 10 apparatus for encoding and decoding standard television signals in subscription television systems. In particular, since the invention utilizes control signals consisting.of 32-bit binary pulse trains to identify the various authori'zed:
subscribers each having a different code combination, it provides a very high security system thereby preventing unauthorized viewers from unscr.ambling of the video sig-nals. Moreover, the audio signals are also scrambled to increase' the security of the system and to deter most ' .
unauthorize~ viewers by convertiny the analog audio signals to coded digital audio signals. Additionally, the present invention includes control means for continuously enabling decoder means at the various subscriber stations ~hereby any or all of ~hese decoder means bPcome selectively disabled or "locked out" if it does not receive appropriate control 2S signals frpm the broadcaster periodically before a pre~
determined interval of time has elapsed.

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BRIEF DESCRIPTION OF THE_DR~INGS

These and other objects, features and advantages of the invention, as well as the invention itself, will become more apparent to those skilled in the art from the following detailed description when read in conjunction wi~h the accompanied drawings in which like reference numerals indicate like or corresponding parts ~hroughout the several views wherein: . .
Pigu~e 1 lS a simplified, over-all block diagram of a subscription television system in accordance with.the presenk invention;
Figure 2 is a block diagram of a television transmi~ter at the broadcaster site illustrating the means for encoding or scrambling the standard television signals~
embodying the present invention;
- ~igure 3 is a block cliagram of a receiver at the subscriber site for decoding or unscrambling the encoaed television signals received from the transmitter shown i.n Figure 2, according to the present invention;
Figure 4 is a block diagram of telephone communication circuitry for interconnection between .he transmitter and receiver, employing the novel methods of the present invention;.
Figure S is a simplified block diagram depicting - circuitry suitable for use as the adder networks 80, 136 Q~
Pigures 2 and 3;

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Figure 6(a) is a time-amplitude graph of a conventional, normal scanning line in a television signal;
Figure 6(b) is a graph similar to that sho~.m in Figure 6(a), in which some video signal portions havea been.
randomly inverted, according to the present invention;
Figure 7 is a spectral distribution of the signais transmitted in the present invention;
Figure 8(a) is an example of a control signal consisting of 32 bits, according to the present invention;
Fisure 8~b) is an example of a digitized aural signal consisting of 11 bits, employed in the present invention;
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Figure 9 is a schemat.ic diagram showing circuitry suitable for use as the shift register 122 of Figure 3;
lS. Figure 10 is a more detailed schematic block diagram showing circuitry suitable for use in certain of the blocks of Figure 3;
Figure ll(a) is a schematic diagram illustrating circuitry which may be employed in certain of the other blocks of Figure 3;
Pigure ll~b) is a schematic diagram illu5 ~rating in more detail the circuitry which may be used as the video switching amplifier 88, Figure 12 is a schematic diagram showing circuitry suitable for use as the shift register 152 of ~igure 3;
- Figure 13 is a block dlagram depicting the circuitry suitable for use as the blocks 146, lS0 shown in Figure 3;

~ ~55~2 .~igure 14 is a schematic diagram illustrating circuitry which may he employed in certain of the blocks of Figure 4;
Figure 15 is a schematic diagram illustrating suitable circui.try for use as the gating circuit 1~6.of ~igure 4;
Figure 16 is a schematic diagram showing circuitry sui,table for use as the switches 156 of Figure 4, Figure 17 is a schematic'diagra.m illustrating cix~uitry which may be employed,to control the lights 180 and 186 of Figure 4; and '. ' Figure 18 is a schematic block diagram ill~lstrating circuitry.which may be employed as the master clocks 66 and 130 shown in Figures 2 and 3.

- DET~ILED DESCRIPTION OF, T~E PREFEP~RED_E~IBODIMEN~ , Referring now in detail to the drawings, ~igure l : illustra~es a simplified, over-,all block diagram o~ a ~ub-scription television system according to the present inven~ion.
: It should be understood that this system can be utili2ed in 2Q various forms of television transmission and recepticn~ in- '' . . .
~- . cluding over-the-air or cable television. Like refe-ence numerals have been employed thrc~ughout the variouc drawinss to cesignate like parts~ ' . .In Figure l, the subscriptlon television s~stem '-~ 25 designated'generally b~ reference numeral 10 consist~ng of a transmitter section 12, a receiver section 14, and telephone , communication circuitry 16 located at the receiver sectlon .
': -1 ~59~2 14 for communication with the transmitter section 12. A .
central computer 18 is used to store informa~ion signals identifying the various authorized subscribers and sends out these information signals to a transmitter 20 for transmission over-the air via antenna 22. A synchronizing - (sync) genera,tor 24 is connected to the computer 18 for synchronizing th~ information signals sent from the computer to the horizontal scanning rate used by a television program source such as television camera 26. In order to prevent ' 10 unau~hori~ed viewers from receiving the telecast, the signals from the television camera 26 are processed by a code converter 28 along with the same information signals from the computer utilized to identify the authorized sub-scribers, which modifies the signals in such a way to be unintelligible to unauthorized subscribers. These signals are then sent over-the air via a transmitter 30 2nd antenna .~ 32. Analog audio signals from a sound source such as microphone 34 can also be processed or modi~ied in th~: converter 28 by sending th.e audio signals through an analog~
to-digital converter 31 to produce digitized audio signa : The scrambled audio signals from the code converter 28 are : also transmitted via the transmitter 20 and ~ntenna 22.
.The scrambled television signals, the scra~bled audio signals and the information signals are received by antenna 36 These signals are then delivered to an ~ tuner 3~ coupled to an intermediate frequenc~ (IF) amplifier and ' : -13~.
' 115~9~2 dete~tor 4Q which detects the scrambled television signals and to an ~P tuner 42 coupled to an IF amplifier and detector 44 which detects the scrambled audio signals and the in~or-mation signals. The scrambled television signals are sent.' to a code converted 52 for re-processing~ The information . signals from,the detectvr 44 are sent to a comparison circuit 46 to determine if one of'the information signals matches - , the uni~ue address associated with a particular subscriber . stored in read-only-memory 4~O These same information signals serve as control signals and are delivered to a code lock- .
out circuit 50 as is the output of the comparison circuit 46. When there is a match,~the co~parison circuit 46 activates the circuit 50~to allow.the control signals'to pass thxough to the code converter 52 which unscrambles the television signals from the detector 40 and the scrambled audio signals ~rom the detector 44. The unscramblèd television signals are sent to a modulator 54 ~or converting the television signals to a frequency corresponding an unused numbered channel on a conventional.television xeceiver 56. The ~: 20 digitized audio si.gnals from the code converter 52 are also sent to the modulator 54 for transmission on the receiver 56 via a digital-to-analog converter 58 for co~verting the digitized,audio signals to t}le oriyina,l analo~ audio sig-nals.
Each subscriber can select the programs he wishes to view by simply depressing switches or buttons (not shown) -14- .

~ ~5~2 associated with the telephone communication circuitry 16 . located at the receiver section 14. The selections are transmitted to the computer 18 directly by telephone lines 62. It should-be apparent to those skilled in the art that the present subscription television system can be easily ~onverted to conventional cable television systems by simpiy replaciny the antennas 22, 32 and 36 with an appropriate, interconnected coaxial cable (not shown)O
; The .~ransmitter section 12 shown in Figure 1 will now be described in greater detail with reference ~o Figure.

2. The central computer 18 is utilized t~. generate randomly a sequence of codes, each one representing a particular account number or address o~ an indlvidual subscriber. ~ach of the codes is a pulse train of 32 bits, each or the bits being either high ~"1" state) or low ~"0" state), exce?t ~ that the first bit is always made to be low and the last bit ; is always made to be high so as to facilitate the detection.
and synchronization b~ the circuitry in the receiver section 14~ Thus, the number of different subscxiber codes available 20 is 23 or 1,073,741,824 since this is the number of possible combinations of thirty bits each of which can be either high or low.
.These codes are selected by the computer 18 such that each of the eligible subscriber's code is transmitted in a pre-determined sequence and is then repeated on a continuous cycle thereafter. Each of the 32-bit codes are , . ~ . ' ' ;

g ~ 2 addresses of the individual subscribers located in the broadcaster~s coverage area~ When these transmitted codes are reprocessed at the receiver station 14, it produces the .xequired information that it utilized to determine the code used to encode or scramble both the aural and visual portions - of the broadcasted television program.
The broadcast of these 32-bit codes or enoded signals is synchronized to the horizontal scanning rate produced,by the sync generator 24 as is conventionally used by the television camera ?6 in ~he standard television.
studio. The sync generator 24 provides a.pulse pattern at the rate of 15, 750 time-s per s,econd (15,734 for color).
which corresponds to 525 horizontal scan.lines in the visual' raster of a conventional television picture traced by an electron heam of varyins int,ensity from the top to the , bottom of the picture in lf30 o:E a second. The horizontal sync pulse or signal output of the generator 24 is,'connected via lead llne 60 to the inputs of the televislon,camera 26 and a monostable circuit (one-shot) 64. The monostable ZQ circuit allows adjustment in the pulse width of the hori20ntal sync signal, and its output controls a master clock 56 having pre-set frequency of 16~128 ~IHz (16.111 ~IHz for color) and provides data request signals to the computer 18.
; The output pulses from the master clock 66 are phase-locked to the horizontal scanning rate. The vertical sync pulse or signal output o the generator 24 is connected via lead lin~

9 ~ 2 .
68 to an inpu~ of the television camera 26 and to monostable circuit 70 in which the width of the vertical sync pulses are adjusted and are used to provide lnterrupt request signals to the computer 18.
The computer sends out randomly the various 32 - ..
bit binary subscriber codes on line 72 in a parallel manner to a parallel-to-serial converter 74. Since a dif~erent - -32-bit code is sent out by the computer 18 at the rate of the horiz.ontal scanning frequency o 15,750 times per second.
as provided by the sync generator 24, this means that 94~000 inaividua:L subscribers can be selectively controlled to unscramble the transmitted signals.every minute. The converter 74 transorms the codes from parallel into a seria~
sequence for modulation of ~he transmitter 20 via a ~reqi~ency : 15 shift ke~.ing (FSK) FM modul~tor 76. These same 32-bit codes~
of the various subscribers are also made available on line ~. . .
78 and are processed into corresponding 4-bit codes or ;~ words.by an adder network 80. These 4-bit words .contain ~ .
the informat.ion to be utilized in determining the encoding . or scra~bling pattern of the video and sound portions of the broadcasted signals. The details of the adder network 80 will be discussed more fully hereinafterO
.The coded signals from the output of the adder network 80 are coupled to datainput of a D-type gating flip-flop for synchronization with the horizontal scanning .
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rate'which is connected to the clock input of the ~-~ype flip-flop via lead line 84. The output of the flip-flop 82 contains the encoded pattern which scrambles the visual and aural portion of the televised signal via an active li~e gate,86 and a gated'video switching amplifier 88 and an additional adder network 100, respectively. The switching amplifier 88 consists actually of three separate amplifiers, one being a non-inver,ting amplifier 90, a second being an inverting amplifier 92-and a thixd ampli-fier 94 determining whether the output of the non-inverting amplifier 90 or the inverting amplifier 92 is fed to its , input. (See Figure ll(b)). ~Since the active line gate 86 drives the'switching amplifier 88, the output of the switch-.
ing amplifier will be dependent upon the binary stateof the , active line gate 86, which is either in the "1" (high) or "O" (low) states. The line gat:e 86 is actuated only during the portion of the televised si.gnal that contains the actual visual or picture portion and i.s de-activated during the synchronization intervals. When the output of the line gate 2~ 86 is in the high state, the video portion of the televise~
signal is sent through the non-inverting amplifier 90 and -the output of the switching amplifier 88 is not inverted.
~owever, when the output of the line gate 86 is in the low state the video portion of the televised signal is inverted.
2~ Since the output of the adder network ~0 passed through the active line gate 86 switcles ~etween the two binary states 1 ~5~9~2 on a'pseudo-random basis~this causes some of the video signal portions at the output of the switching amplifier ' 88 to be positive and some'to be negative, which creates a mosaic quality in the picture. This scrambled picture is very unpleasant and completely unintelligible to the - unauthorized viewers. The output of the switching amplifier 88 having the scrambled picture is coupled to an AM
modulator 96 for amplification and modulation. The output of the modula~or 96 is then sent to the ~ransmitter 30 for broadcasting the'scrambled p'icture via the antenna 32.
: . . . . .
As is well-known, the origi'nal visual information and the chrominance informa~ion originate in the television camera 26 and a chromatic (color) sub carrier generator or phase modulatox 98 respectiv~ly. As previously mentioned, 15~ ~he horizontal and vertical synchronation signals sent to the central computer 18 are also used to synchronize the horizontal and vertical scanning rate of the television camera 26. A typical audiosource originating the micro-phone 34 at the broadcaster's site or a similar audio 2Q source such as a tape recorder, film chain, phonograph record and the li~e is also encoded or scrambled so as to increase the security of the system by first converting the original aural signals (analog form) to digital pulse trains each consisting of 11 bits via the analog-to-digita .

:

1~l5~9~2 converter 31n Each of the bits are eithex high ("1l' state) or low ("0" stateJ, but the first bits are always made to be low and the last bits are always made to be high so as to facilitate the detection and synchronization by th~ circuitry .5- in the receiver section 14. Then, these pulse trains o~
the digitized aural signals are added binarily with the 4.-bit binary outputs of the D-type flip-flop 82 resulting from the addèr network 80 via the additional adder network 100. These resultant ll-bit binaries are converted to -serial pulse trains by a shift register or parallel-to-: serial converter 102. These serial pulse trains are coupled to a frequency shift keying~M modulator 104 for amplifica-tion and modulation before being sent to the transmitter 20 and transmitting antenna 22 for broadcast.
; lS . In additiont a second audio source 106 can beprocessed in an unscrambled form by an FM modulator 108 - for transmission ~ia the transmitter 30 and the transmittin~
antenna 32. The second audio source 106 is refe~red to as a "barkçr" source and canbe heard by all of the television : 20 . receivers. It is utilized for encouragîng the viewers to use the programming of the subscription television system : . and i5 ~vailable for announcement and to promote mar~eting of the subscription tele~ision programs to potential pur-chasexs or other suitable use.
A control terminal 110 is connected to the computer lB for controlling manually the enabling and .

~2 disabling of ~arious subscribers. A modem 112 is coupled also to the computer 18 for transferring the program .' requests from the various subscribers sent on the tele-phone line 62 as will be explained in detail in connect;.on, S with the telephone communication,circuitry 16~-,. The receiver section 14 shown in Figure 1 o~ the drawings will now be discussed more fully with reference'to Figure 3. Eac,h subscriber to the subscription television system is provided with a,housing or box-type enclosure (not shown) containing all of the receiver-cixcuitry in the receiver section 14 including the telephone communication circuitry 16 for-operative connection to'his conventional television receiver 56. The enclosure is typically place~
adjacent or on top of the subsc:ri~er's television receiver~
The enclosure is interconnectecl between the subscri~er;s receiving antenna terminal connections and the television receiver 56. Power is supplied to the enclosure via a :' ' . 120 VAC power input terminal located on the encl~sure.
This e~cl.osure is further'connected to a telephone termin~.
:~ 20 outlet (not shown) conven'tionally supplied ~y a local telephone utility company for'communication with the broad-caster to request service of'the programs desired vi2 the '.
telephone communication circuity 16, as will be discussed more,fully later~
All of the transmitted signals ~rom the transmitting antennas 22 and 32 and all of the other conventionai, ~nscram~led .

-21- . -television channel signals are received as incoming.signals on the receiving antenna 36. It should be recalled that the transmitting antenna 22 is sending out two separate sets of digitally excited frequency shift key.ing data signals, S namely, the digital control signals each having a pulse train of 32-bits and the digital audio signals each having a pulse train of ll-bits. The other transmitting an~enna 32 is sending out the encoded or scrambled video signal.s, the normal chrominance signals, and the "barker" audio signals.
The incoming signals are now processed by s?litting them into three paths at an RF splitter 114. One path drives the RF tuner 38 coupled to the IF amplifier and detector 40 ~hich extracts all of the scra~led video, normal chrominance, and "bar~er" audio signals. A second path is processed by the RF tuner 42 coupled to the }:F amplifier and detector 44 for removing all of the digital audio signals and digital control signals. A third path via lead line 116.is util~.zed to receive the other unscrambled channel signals when the subscription television system i5 not in use.
It will be apparent that in svsLems dealins with scrambling and unscrambling of signals -the methods used in unscrambling are functiona~ly complementary to the vnes used in the scrambling process, and that the unscræ~bling and scrambling processes have to be com~let~ly syncnroni~ed.
Thus, many of the circuit componen~s that will be discussed .

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hereinafter in the receiver section 1~ are simiiar in operation to those previously mentioned in the transmitt-ing section 12.
- The scrambled video signals from the output of the detector 40 is connected to a gated video switching -- amplifier 118 similar to the switching amplifier 88 for unscrambling and restoration of the picture back to a normal image. However, this can occur-only if proper decoding signals controlling an active line gate 120 similar to the line gate 86 will cause inverting or non-invertiny of the video portions of the televised signals on a line for line basis in exact correspondence to the scrambling by the active line gate 86. The reprocessing of the control signals to generate the decoding signals will now be explained in detail.
An output containing the control signals from the detector 44 is sent to a serial-to-parallel converter or shift register 122 and to a pulse detector 124. Since the first bits of the incoming pulse train con~rol signals are always beginning with a low level, the pulse detec~or 124 `~ i5 utilized to sense the shift from a high level to a low - le~Jel. When the ~hift i5 detected, the output of the detector 124 drives a monostable circuit 126 (one-shot) to synchronize the receiver circuitry with the transmitter horizontal scanning rate of 1,57~Hz and also to permit adjustment o~ the pulse width from the detector.

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~ ~5~952 Once the shift is detected, the monostable - circuit 126 initiates the counking of a divide-by-eisht counter 128 (- 8). The clock rate of the counter 128 is provided by a master clock 130 similar to the clock 66 . having a pre-set frequency of 16.128 MHz which is actuaily 16 times greater than the pulse rate of the incoming control signals and is phàse-locked to the horizontal scanning rate o~ the transmitter section 12~ Thus, after ei~ht clock pulses are counted, the middle of the first bit or pulse of a 32-bit incoming control pulse train will be .-at the input of the shit register 122O At.this point, a transfer ~ulse will be generated to shift the first bit into the shift register 122 for storageO
The output of the counter 128 is coupled to a - 15 divide-by-16 counter I32 ~. 16~, which is in turn connected to a divide-by-32 counter 134 (. 32). Subsequ2nt to the storage of the 1rst bit, the counter 128 is stopped and the counter 132 is activated to count so that 16 pulses later~ the shift register-122 will have at its input the middle portion of the second bit of the 32-bit pulse train.
Once again, a transfer pulse will be generated to sni't now the second bit into the shift register 122 for storaseO The first bit previously stored will be shifted sexially do-~n the shift register. This process is repeated thirty more times . and as a result will cause all 32-bits to be stored in the . -24-~ 1~5952 shift register 122. When the thirty-secondth pulse-is stored, all of the counters 128, 132 and 134 are reset and made ready for the next control signal. Thus, the serial control pulse trains each of a full 32-bits will become stored in the shift regist~r and is made available as parallel sets of.32 data ~its (see Figure 9).
The 32-bits o the shift register 122 are taken out to an adder network 136 which .converts the 32-bits down to a 4-bit unscrambling code. The adder network 136 is identical in operation to the adder network 80 in the `~ transmitter section 12 and produces the 4-bit unscrambling code identical to the 4-bit.scrambling code used to scrarnble the video and aural portîon of the originally.
:~ transmitted signals. A simplified block diagram of the adder networks 80 and 136 are illustrated in Figure S and is compxised of seven fllll binary adder circuits 138 inter-connected as.shown. However, it should be understood that the 32-bit input lines can be interchanged by their bit locations on a pre-determined basis to provide increased security in the system. . Thus, this produces the 4-bit codes at the output of the adder networ~ 13G in a ps.udo-. random scrambling pattern.
A D-type clocking flip-~lop 1~0 is connected ~o . the output of the adder network 136 for holding the ~-bit pattern for the duration of the next horizontal scanning line .
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in order to decode that scanni~g line and all of the audio signals received during tha~ same interval. The flip-flop .
140 drives the active line gate 120 for controlling the switching amplifier 118 to switch its inputs between the inverted and non-inverted inputs in the same sequence , as the encoding operation by the switching amplifier 88 In this mannert the hor.izontal scanning lines at the transmitter section 12 are reproduced at the receiver section 14 so that the received video signals will become restored to the original unscrambled picture.
However, this restoration process. is permitted to occur only if one of the~plurality of 32-bit control signals generated on a pseudo-random basis by the central . computer 18 and transm.itted via the antenna 22 is matched perfectly (bit for bit) with. a unique 32-bit code assigned to a particular subscriber's te:levision receiver 56 ~hich is stored in the read-only-memory (ROM) 48. The transmitted :`~ incoming control si~nals at the output of the dectector 44 are.compared by a comDarator 142 with the unique contents of the ROM 48. The content of the ROM 48 is synchronized with the incoming control signais.by the counter 134.
If the comparison is unsuccessful, the 4-bit code in the D-tyPe 1ip-flop 140 .is prevented to be clockea to the active line sate 120 controlling the switching ampliier 118 to unscramble the video signals. On the other hand, if there is a successful match between one of -26- .

5~52 the control signals and the ROM 48 o the particular sub- -scriber, then a flip-flop 14~ is set and gates a decode enable flip-flop 146 which permits the output signals of the monostable circuit 126 to be sent as clock pulses and set ~
at the horizontal scanning rate to the D-type flip-flop . 140. Unless the clock pulses of the monostabie circuit 126 via lead line 148 are passed through the decode-enable :: flip-flop 146, the D-type flip-flop 140 will not be actl~ated.
Upon a comparison, the output of the flip-flop :~ 10 144 also resets a three-minute timeout ti~er 150 to zero.~en the timer 150 reaches the three-minute mark, it will cause the decode-enable flip-flop 146 to be reset thereby stopping the decoding process as the clock pulses to ~he D-type flip-flop 140 will be bloc~ed by the flip-flop -- lS 146. Thus, continuous decoding is possible and unin.errupted, restored video and aural signals are available to the ~:~ . subscriber only if the comparator 142 causes~the flip-~lop 144 to reset ~he three-minute timer 150 at leas~ once every three minutes.
20 . A second output containing the digitized aural signals from the detector 44 is sent to a serial-to-. . parallel converter or shift register 152 to convert the signals to parallel digital binary form; A subtractor : circuit 154 combines the 4 bit unscrambling codes from the D-type flip-flop 140 with the encoded digitized aural signals.

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The subtxactor circuit 154 operates similar to the adder networks 80 and 136, except that it is actually using 2's complement addition in order to realize unscrambled digiti2ed aural signals corresponding to the ones at the output of the analog-to-digital converter 31 in the - transmitter section 12. The output of the subtractor circuit is connected to the digital-to-analog converter 58 to produce analog signals identical in form to the ..
original audio signals generated by the source 34 at the broadcaster~s site. Thus, it can be seen that decod-ing of the aural sign21s is also dependent upon the D type flip-flop 1~0.
The restored video signals at the output of .
the switching amplifier 118 and the restored audio signals 1$ at the output of the digital to-analog converter 58 are fed into the modulator 54 which converts these signals to a desire~d locally unused V'dF channel (2-13~ as the secured channel. Typically, channel 3 or 6 can be a suitable choice. These signals are combined with all of the other unscrambled televis1on channels recei~ed by the antenna 36 via RF combiner ci~cuit 1550 Tnis allows - view of all the channels on the television receiver 56 - including the secured channel, and selection of the particular channel is achieved merely by turning a channel selector dial (not shown) on the television receiver 56.
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The telephone communication circuitry 16 shown ln Figure 1 of the drawings will now be described in greater detail with reference to Figure 4O E~ch subscriber can selec~ the particular televised program he desires to recieve by depressing one of a plurality of buttons or switches 15~. It should be understood that any desire~
number of buttons or switches can be utilized and connected to pexform various functions. For example, some buttons can be used to select the particular programs to be viewed a~ a desired time while others can be used to cancel or correct errors in the program request. Once a button associated with a particular program is depressed, this selection is transmitted on the telephone lines 62 to a local telephone company's central office ~not shown). In a large metropolitan area, the central office would then communicate with another central office which, in turn, .

relays the program requests to the computer 18 at the broadcaster's site via the telephone lines 62 and the modem 112 (modulator-demodulator3. This communication process will now be discussed more fully.
When a subscriber wishes to receive a particular program, he simply depresses the appropriate button 156 ; which activates a sequence control network lsa to energize a hook-switch relay 160 allowing an"off-hook" or "on-line"
condition with the local central office. ~hen a dial tone is placed on the telephone lines 62 by the central o fice, ~ ~5~

dial ~one detector or filter 162 causes the sequence,control network 158 to transmit dial address stored i~ binary form in a rea~-only-memory (~OM) 164. This ROM 164 is similar to the ROM 48 in the receivPr section 1~ and in fact, can , be the same one. Thexe are two methods of dial addressing which are availahle. First, a multi-frequency tone generator 166 can be used to transmit a designated telephone number employed by the broadcaster to receive automatic telephone ,requests~ The tone generator 166 is known generally by the trademark "Touch-Tone". Alternatively, a programma~le divide-by-n counter 163 can be provided to interxupt current flow in the,relay 160 to diàl the ~esi~nated telephone numhex.
This latter method is known as the dial pulse method o~
dial addressing wherein the number of contact closure interrup-, 15 tions are varied as with a corresponding number on a rotary dlal. A row/column decode 170 converts the dial address from the ROM 164 either into row and column numbered pairs for the tone generator 166 or into 2's complements for loading into the pr~grammable divide-by-n counter 16~ for pulse method dialing via an interface buffer 172 and the hook switch relay 160.
Once the dialing process is completed, the se~uence - control network 158 is arrested and awaits a carrier tone genera`ted by the modem circuitry 112 at the broadcaster's site,. When ~ilter 174 detects the presence of the carrier ~5 tone, it causes the sequence control networ~ 1S8 to address the ROM iG4 storing tne particular subscriber's code consisting ' , :~ ~ 5~2 of 32~bits and to send them out in a parallel sequ~ence of four eight-bit words. A gating circuit 176 is coupled to the output of the ROM 164 and groups the four words for activat-ing a voltage-to fre~uency converter 178 to generate fre-quency shi~t keying modem,tones which contain the sub-scriber's unique-address or account code. Subsequent thereto, the subscriber's request code indicating which of th~ buttons 156 he has depressed is transmitted via the gating circuit 176 and the converter 178. , ' lQ After the request code has been transmitted, the sequence control network 158 stops the gating circuit 176 and then awaits for an acknowledgment tone from the modem circuitry 11~ at the transmitter section 12. When the acknowledgment tone is detected by acknowledgment ton~
filter 175, the sequence control network 158 is discon~ect~d from the telephone lines 62 by the de-energization o~ the relay 160 and lights an acknowledgment light 180 for 15 seco~ds.
~hile only'one acknowledgment light is illustrated, t should ' be clear that any number could be provided to indicaLe which ~0 button corre,spondi~g to a particular request was depressed.
However, if no ~ial tone, carrier tone, or acknowledcm~nt tone is detected or if any part of the dialing sequence is ~ied up beyond a pre~determined time intervalr a time-out timer 182 having its input clock pulses set at the horizontal ~5 scanning rate via lead line 18~ interconnected wi~h 1~2d line 184' (Fig. 3~ will reset the sequence control networ~ 158 and activates a fault light 18~ for 15 seconds.

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~ ~S~52 An isolation transformer 188 is utilized to pro-tect the telephone communication circuitry 16 and isolates it from telephone circuits in the local central office.
A holding current coil 190 draws current rom ~he telephone circuits when the hook-switch relay 160 is closed for causing :. the "off-hook" condition to be detected at the local telephone ccmpany's central office which will respond with a-diai tone~ It should also be apparent to those skille~ in the art that.the account code and request code of the various -10 subscri~ers may be placed on storage devices (not shown?
such as disk drives and magn~tic tapes for use by ~he central computer 18 to gene~ate the account codes of the various authorized subscribers thereby permitting the subscri~ers to view the transmitted scrambled video :: .
. 15 and/or audio signals.
F.igure 6(a) illustrates the time-amplitude relationship of a conventional, normal scanning line whlch includes the composite video and synchronization siynals~
. In Figure 6(b), ~here is shown an example of the trar.smitted ~: 20 scrambled video signal of the present invention wherein certain video portions of the horizontal scan line have been randomly inverted~
Figure 7 shows a spectral distribution in terms o relative maximum radiated field strength of t~e signals transmitted in the present invention verses the frequ~ncy relative to the lowest channel. In par~icular, the graphical ~: .

9 ~ ~
representation of E`igure 7 illustrates in the left-hand half the 6 MHz frequency allocation of a standard televlsion channel as deined by the F. C. C. As is well kno~n, the picture or visual carrier signal, the chromatic su~carrier frequency, and the center of the barker aura~ frequency are located at approximately 1.25 MHz 9 ~ . 83 ~æ, and 5~7~ PlHz, respectively, above the lower frequency end of the telç~ision channel. The right-hand half of Figure 7 depicts the~
control signal center fre~uency and the digital 2ural fre-quency which are located respectively at approximately 9 MHz and 11.25 MHz.
~igure ~la) shows an example o one of the plurality of unique pulse-ooded control signals consisting o~ a 32-bit binary pulse train which are transmitted separately ~y the broadcaster to identify individual authorized subscribers and to provide the information needed for unscrambling o the video and audio signals in the same sequence as used for scrambling. Figure 8(b~ is an example of the scra~bled or coded audio signals, i.e., digitized audio consis.ing of a ll-bit pulse train for increasing the security o~ ~-he system.
~hile the various blocks sho.~n in Figures 1 .nrough 4 may take on various forms, suitable circuitr~ thereror are illustrated in Figures 9 throu~h 18. Althou~h ~hese schematic diagrams are believed to be self-explanatory to ~i~i.-ie skilled .

:

1 ~5~2 -in the art in view of the foregoing.discussion, a brief.
description of the operatLon of each figure is believed to be in order. .-The synchronization oX the entire system is controlled by the master clock 66 of Figure 2, which is shown in more detail on Figure 18. The master clock 66 consists of a voltage-controlled oscillator 192 having a capacitor 194 and an input ~oltage + V. The output of the voltage-controlled oscillator is fed into an inverter 196 whose output is set at a frequency of 1~.128 MHz. :
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The output of the inverter 196 is fed to all places re-quiring this frequency output and to a counter 198 (~ by 1024). The frequency at the output of the ~ounter 198 designated by the lead line 200 is 15,750 Hz which is . 15 delivered to one input of a.phase-lock circuit 202. The other input of the phase-lock circuit 202 designated by lead line 204 is the horizontal sync p~llse ~rom the . generator 24 ~Figure 2)~ Th~s, the voltage output of ~he . phase-lock circuit 202 on lead line 206 ~aries via le~d line 205 until voltage-controlled osclllator 192 is phase-locked to the horizontal scanning rate.
.~ Referring now to Figure 9 of the drawings, there ; ~is shown .in more detail the circuitry of the shi~t register : `
122 of Fiyure 3. The output containing the control signals ~rom the detector 44 on lead line 208 ~Figure 3) is eonnected , . . .
to the lead line 208'. The shift reg.ister is com?osed of-a ~ ' ' " ' ' .

plurality of J-~ flip-flops 210 connected serially and a plurality of inverters 21~. The output of the flip-flops 210 labeled 2-231 are connected to the corresponding inputs of the full adders 138 on Figure S. In order to shift the full 32-bits of the control pulse trains into the ~lip flops 210, the transfer pulse is delivered o~ the lead line 214 which is connected to the lead line 21~' in Figure 10. The control signals on the line 208'.are also sent via line 216 which is connected to the lead line 216 ' on Figure lQ for reception by the pulse detector 124. The output of the pulse detector on its lead line 218 is utilizecl to reset the counters 128, 132 and 134. These counters are formed by tèn J K flip-flops 220. Tne clock input to the counter 128 is.on lead line 222 which is connected : 15 to the 16.128.MHz output of Figure 18.
As will be recalled, the clock frequency is actually 16 times g~eater than t.he pulse rate of the incoming control signals. Therefore, a~tler eight clock pulses are counted the middle of the first bit of the 32-bit incoming pulse .train will be at the input of the flip-flop 210 desig~a,ed by lead line 2240 However, in practice it has be~n encountered that only four clock pulses need to be counted so as .o be in the middle of the ~irst bit. The reason i5 beca~se of propagation. delays and other inherent delays associated with electronic circuitry. Thus~ a NAND gate 226 is inter-connected so as to genexate a transfex pulse on l.S 1 2d line , ' ~ 1~5~3~2 214' after the fourth cloc~ pulse and each sixteen pulses thereafter~ In this manner, the entire 32-bits of ~he serial control pulse train is transferred into the flip-flops 210 of Figure 9.
Prior to the transfer of each bit, a comparision of such bit is being made with one corresponding bit o~
the unique 32-bit code stored in the read-only-memory 48 byt~e comparator 142. The output of the comparator is coupled to the flip-flop 144 whosa outpu~ i5 connected- to an input of NAND gat~ 228. When there is a co~parison, the output of NAND gate 228 on its lead line 230 gate~ the decode~and-enable flip-flop~146, which is shown in more de-tail on Fig~re 13.
. The last J-K flip-flop 232 and the NAND ~ates 234 in the counter 134 are used to reset all of the counters 128, 132 and 134 after the last pulse or thirty-secondth pulse of the 32~bit control pulse train. Then, the ~ounters are ready to sample and compare the next control pulse train.
In Figure ll(a), there is shown in more de~ail the . circuitry of the blocks 120~ ana 140 in Figure 3 of the drawings. The NAND gate 236 has its one input designated _; by lead line 238 connected to the output of the decode-an~- -enable fl.ip-flop 145 designated by lead line 238l t~igure 13).
: The other input to the NAND gate 236 designated by lead line ~5 240 is coupled to the clock rate o~ 15,750 Hz.. The output of the NAND gate 2 36 is connected to one input o~ the active~

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1 ~5~9~2 ;
line gate 120 and to the`clock input of the D-type flip-flops 242. The other inputs designated by lead lines 244 through 250 are connected to the output of the adder net-work 136 shown in Figure 5 and desi~nated by 2 through 23. The output of the D-type flip-flop 140 is connected to the subcontractor circuit 154. The other input-to the subtractor circuit is the digitized aural signals from the output of.the shift register lS2 on the lead lines 252.
The output of the subtractor circuit 154-is coupled to the input of. the digital-to~analog converter 58 whose ~utput on lead line 254 is connected to one input of the.modulator 54 .
T~e other input to the active-line gate 120 on its.
lead line 256 is from the 16.128 MHz output of the master clock on Figure 18. The active line gate includes ten 3-K flip- .
flops 258 which are connected in a serial manner~ As pre-viously discussed, the active-line gate 120 will keep the video switching amplifier 118 in the non-inverting condition,-except during the active portion of the horizontal scanning line. The output of the active line gate from N~lD sate 260 is connected to amplifier 117 bf the video switching am?lifi~r . 118. The other input to the amplifier 118 on its lead line 262 is from the output of the IF amplifier and detector 40 containing the scrambled video signals. The output.of- the amplifier 118 designated by lead li.ne 264 is connected to the other input of the modulator 54.
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In Figure 12, there is shown in more deta~l the circuitry of the shift register 152 of Figure 3. The output containing the digitized aural signals from the detector 44 on lead line 266 (~igure 3~ is connected to .
the lead line 266'~ The shift register is composed of . a plurality of J-K flip-flops 268 connected serially.
The output of the flip-flops 268 labeled 2-2l are connected to the inputs of the subtractor circuit 154 on the lead lines 252 (Figure 11). In order to shift the full ll-bits of the digitized aural s.ignals into the flip-flops 268, the transfer pulse is deli~ered on the lead line ~70 connected to the output of ~NAND gate 2i2. The shift register includes counters 274, 276, and 278. The coun~er 274 is a divide by-eight (. by 8) countex having its clock input coupled to the aural clock rate;output in Figure 13 via lead line 280. In actual practice, it can be seen that the NAND gate 272 is interconnected so as to generate a .ransfer pulse after the fourth clock pulse and each sixteen pulses .
thereafterO This is because ~nly four clock pulses are 20 - needed to be counted due to propogation delays in electronic circuitry hefore the middle of the first bit of the ll-bit digitized aural 5ignals is at the input of the flip-~lop 268 designated by lead llne 2820 In this manner, the entire ll-bits . of the aural signal is txansferred into the flip-flops 268 25All of the counters 274, 276 and 278 are ~ormed from a plur~l~ty of J-~ fllp-~lCOS 84- The counter 276 is . ' ' . , ' . ,'' .

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connected to the counter 274 so as to form a divide-by-.
sixteen (. by 16) counter. The counter 278 is inter- ' connected with the NA~D gate 286 so as to ~orm a di~-ide-by-ll counter so that all of the counters are reset by the NAND gate 286 after the last pulse or llth-bit of the.
. digitized aural signal'has been conducted~ .
Figure 13, there is shown a divide-by-N counter 288 having the various clock rate outputs. The input to the counter 288 designated by lead line''290 is from th~ , output of the counter 19 8 on its lead line 290' in Figure 18. The three-minute output from the counter 288.is uSed to reset the decode-and~able flip-flop 146 after thxee minutes of time has elapsed to stop further decoding by th.e D type flip-flop 140 unless'there is a comparison between .
one,o~ the control signals with the unique address of the read-only-memory 48 prior to that time. The 30-second output from the counter 238 is connected to the lead line 184 tied to the inpu~ of the time-out timer 182 in Figure 4.
The output labeled "clock-rate 2 " is connected to the lead . line 294 in Pigure 14, and the output labeled '~clock-rate 213l' is connected to the lead line 296 in ~igure 14.
_ In Figures 14-17, there is shown in more detail suitable.circuitr~ which may be used for the telephone 'communication circuitry shown in Fiqure 4 of the drawings~
In Fiyure 16, there is shown seven button5 or switches 298 for generating the program request code signals at the outputs '

3~

of the NAN~ gates 300O The output of the NAND gate 302 - designated by lead line 304 is connected to the lead 304' on Figure 14 to initiate the telephone dial up sequenceO The lead line 306 is used to control the iele-S phone re~uest code which is connected to lead line 3~.6' on Figure 14,. and ~he lead line 308 is used to re~et the telephone request code which is connected ~o lead iine 308' also on Figure 14O
.In ~igure 15~ there is shown in details o~ the gating circuit 176 composed of a plurality of J-K ~lip- .
flops 310 and NAND gates 312 and 314. The input to the NAND gates 312 are from the xead-only-memory 48 and the program request code si~nals from the NAND gate 300.
rrhe ~ransfer of data into the gating circuit is con-15 . trolled by the lead line 316.whi.ch is connected to the lead line 316' on Figure 14. The output of the gating circuit is designated by lead line 318 which is connect2d to the input of the voltage-to-frequency converter 178~
In Figure 14. ~ere is shown ~he detailg of the : 20 sequence control network 158 and the programmable coun~er 168. The sequence control network includes 3-K ~lip-flops ~-~ 324. Each of the outputs of the flip-flops is connected to the read~only-memory 48 and the NAND ga~e 322 O! tne counter 168.
In Pigure 17, there is shown a typical ligh~
driver circuit for lighting the light 180 to indicate a fault and to ligh~ the light 185 to indicate receip~ o~ the acknowledgement tone. Illumination of either lig~t 180 or 186 is for fift en seconds as controlled by lead line 181 tlS sec. output) which is connected to lead line 181' on Figure 13~ While there has only been one suh circuit ~ 1~59~i~
shown, it should be undexstood that seven are used in this example to correspond to the number of swîtches 298.
It will be understood from the foregoing description that the present invention significantly advances the state of the art of cod~ng and decoding of standard television signals which allows the reception thereof in an intelligible manner only by authorized subscribers~
In particular, the scrambling of th video signals in the invention is effected by inversion of th~,video signals of some horizontal scan lines on a pseudo-random basis to -pr~duce a picture having some video signals inverted and others not inverted. The scrambling of the audio signais is effected by conversion o~ analog audio signals to coded digital audio signals. Telephone communications circuitry can also be provided so that the subscribers can request their programs to the broadcaster via a telephone interface.
While there has been illustrated and described - what is at present to be a pre~erred embodiment o,' ~e present invention, it wil~ be understood by those skilled in the art that various changes and modifications ma;~ be made and equivalence may be substituted for elements thereo~
,~ without departins from the true scope of the inventi~n.
In addition, many modiications may bP madel,to adap~ a particular situation or material to the teachings OI the invention without departing from the central scope t~ereof.
Thereforc, it is intended that ~is invention not be l~'mited 1.

9 ~ 2 ~o the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but tha~ the invention will include all embodiments falling ~ithin the s_ope or th~ app-nded c ~i~s.

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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A subscription television transmitter for generating signals having a program video portion and a program aural portion in a non-standard format to enable reception of both program video and program aural portions in an intelligible manner only by authorized subscribers; said television trans-mitter comprising:
a) encryption code signal generating means;
b) at least one carrier signal generator means adapted to convey by cable or over-the-air transmission the program video and program aural portions and the encryption codes signal from the transmitter to authorized subscribers;
c) means for digitizing the program audio signal;
d) means responsive to the encryption code signal for digitally encrypting the digitized program audio signal from the digitizing means;
e) means for combining the encryption codes signal, the digitized and encrypted audio program signal, and a video program signal, with the carrier signals whereby the encryption codes signal, the digitized and encrypted audio signal and the video signal can be individually separated at a receiver.

2. A subscription television transmitter for generating television signals having a program video portion and a pro-gram aural portion in a non-standard format to enable reception of both program video and program aural portions in an intel-libible manner only by authorized subscribers; said television transmitter comprising:

a) authorized subscriber address codes signal generating means, b) at least one carrier signal generator means adapted to convey by cable or over-the-air transmission the pro-gram video and program aural portions and the subscriber address codes signal from the transmitter to authorized subscribers;
c) audio encryption codes generation means responsive to the subscriber address codes signal;
d) means for digitizing the program audio signal;
e) means responsive to the audio encryption codes for digitally encrypting the digitized program audio signal from the digitizing means, f) means for combining the address codes signal, the digitized and encrypted program audio signal and a video program signal with the carrier signals whereby the address codes signal, the digitized and encrypted pro-gram audio signal, and the program video signal may be individually separated at a receiver.

3. The subscription television transmitter of Claim 2 including:
a) video scrambler codes generation means responsive to the subscriber address codes signal;
b) means responsive to the video scrambler codes for scrambling the program video signal whereby the subscriber address codes signal functions not only to identify authorized subscribers, but additionally, as a key to generate encrypted audio and scrambled video.

4. The subscription television transmitter of Claim 2 wherein the subscriber address codes signal from the address codes generating means is comprised of successive address codes, each address code having a plurality of binary digits, and wherein the audio encryption codes generating means includes binary adder means responsive to the address codes wherein the address codes binary digits are combined to pro-duce encryption codes having fewer binary digits than the address codes.

5. The subscription television transmitter of Claim 2 in which the digitally encrypting means includes adder means wherein the audio encryption codes are added to the digitized program audio signal to produce the digitized and encrypted program audio signal.