`
`3,924,059
`1111
`1191
`United States Patent
`
`Horowitz [45] *Dec. 2, 1975m
`
`[54]
`[75]
`
`PAY TELEVISION SYSTEMS
`Inventor:
`Irving Horowitz, Eatontown, NJ.
`
`3.081.376
`3440,3323
`
`Loughlin et all ...................... 178/51
`3/1963
`4/1969 Walker .............................. ..
`l78/5.l
`
`Primary Examiner—Maynard R. Wilbur
`Assistant Examinerks. C. Buczinski
`Attorney, Agent, or Firm—Michael S. Striker
`
`[57]
`
`ABSTRACT
`
`Reference pulses of opposite polarity to the horizontal
`sync pulses are added to the composite television sig-
`nal just preceeding each horizontal sync pulse. The
`video portion of the signal is inverted for randomly se-
`lected fields. Coding bursts are added to the co'mpos-
`ite signal to indicate whether subsequent field is in-
`verted. Transmitter clamped to reference pulse level.
`Reference pulse used for AGC in decoder Video Por-
`tion of received signal
`inverted in accordance with
`Coding burstS- Audio program signals encoded by
`modulation on suppressed carrier centered above
`audio range. Barker signals transmitted on normal
`audlo frequenc‘es-
`
`[73] Assignee: Teleglobe Pay TV System Inc., Rego
`Park, New York, N.Y.
`The portion of the term of this
`patent subsequent to July 16, l99l,
`has been disclaimed.
`
`1.
`
`1 Notice:
`
`[
`
`[22]
`Filed:
`Dec. 28, 1973
`_
`[211 Appl' NO" 429’216
`Related US. Application Data
`[62] Division of ser. No_ 227,582, Feb' 18, 1972, Pat. No.
`3,824,332.
`
`
`
`. l78/5.1; I78/DIG. 13
`[52] US. Cl................ ..
`[51]
`Int. C1.2 ................................. .. H04N 1/44
`[58]
`Field of Search ..................... .. 178/5.1,DIG. 13
`
`[56]
`
`References Cited
`UNITED STATES PATENTS
`
`2,972,009
`
`2/1961
`
`Roschke ............................ .. 178/5.1
`
`6 Claims, 16 Drawing Figures
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`US. Patent Dec.2, 1975
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`PMC Exhibit 2159
`Apple v. PMC
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`PMC Exhibit 2159
`Apple v. PMC
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`PMC Exhibit 2159
`Apple v. PMC
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`Apple v. PMC
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`PMC Exhibit 2159
`Apple v. PMC
`IPR2016-01520
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`

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`US. Patent Dec.2, 1975
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`Apple v. PMC
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`PMC Exhibit 2159
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`US. Patent
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`Dec. 2, 1975
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`PMC Exhibit 2159
`Apple v. PMC
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`

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`US. Patent
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`Dec. 2, 1975
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`Sheet 7 of 12
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`PMC Exhibit 2159
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`Apple v. PMC
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`

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`US. Patent
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`Dec. 2, 1975
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`PMC Exhibit 2159
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`Apple v. PMC
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`PMC Exhibit 2159
`Apple v. PMC
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`Page 13
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`

`

`1
`
`PAY TELEVISION SYSTEMS
`
`3,924,059
`
`5
`
`2
`all synchronizing and video portions, is transmitted, but
`the reference pulse occupies the levels normally associ-
`ated with the horizontal synchronizing signals. The
`This is a division, of application Ser. No. 227,582
`width of the reference pulse is not sufficiently wide to
`allow synchronizing of a receiver onto said reference
`filed on Feb. 18, 1972, now Pat. No. 3,824,332.
`ulse.
`p The transmitted signal is further encoded by revers-
`BACKGROUND OF THE INVENTION
`ing the polarity of the video signal during randomly se-
`This invention relates to pay television systems. It is
`lected fields. Encoding bursts are injected into the
`the object of such television systems to encode the sig—
`nal at the transmitter in such a manner that a receiver 10 composite signal prior to transmission to indicate
`cannot furnish a picture unless a decoder is activated.
`whether or not the subsequent field has a video portion
`by the subscriber. Activation of the decoder of course
`to be inverted.
`leads to charges for the program received. In known
`The audio portion of the program is encoded by mod—
`methods and arrangements of the above-described
`ulating said program audio signals onto a suppressed
`types, the transmitted signal is encoded by varying the 15 carrier. In a preferred embodiment of the present in-
`timing between the video and synchronizing compo-
`vention, said suppressed carrier is derived from the
`nents, that is selectively retarding or advancing the
`horizontal synchronizing signals and has a frequency
`video component relative to the synchronizing signals.
`equal to twice the horizontal line frequency. The fre-
`Key signals are then transmitted which indicate the
`quency range normally occupied by the program audio
`necessary retardation or advance of the signal which 20 signals is used to transmit a barker signal giving infor-
`must be effected in the receiver in order that the final
`mation about the program to the subscriber.
`system furnished to a paying subscriber may have the
`The novel features which are considered as charac—
`video portion of the signal in the correct relationship
`teristic for the invention are set forth in particular in
`relative to the synchronizing portion.
`,
`the appended claims. The invention itself, however,
`In other known systems of the above—described type, 25 both as to its construction and its method of operation,
`the coding operates on the synchronizing portions of
`together with additional objects and advantages
`the signal. For example, the field synchronizing compo-
`thereof, will be best understood from the following de-
`nents of the television signal may be frequency modu-
`scription of specific embodiments when read in con-
`lated on the picture carrier, while the line synchroniz- 30 nection with the accompanying drawings.
`ing components are coded and then transmitted to sub-
`scriber receivers concurrently with the sound-signal
`BRIEF DESCRIPTION OF THE DRAWINGS
`components on a sound carrier. Key signals indicating
`FIG. 1 shows the unencoded and encoded television
`the coding schedule of the line synchronizing compo-
`signals of the present invention;
`nents are transmitted to subscriber receivers over a
`FIG. 2 shows the vertical blanking interval of an en-
`separate channel. Both of the above-described systems 35 coded television signal in accordance with the present
`have definite drawbacks. The first lends itself rather
`invention;
`'
`readily to unauthorized decoding, the second requires a
`FIG. 3 is a block diagram of the encoder unit;
`great deal of extra equipment since a standard televi-
`FIG. 4 is a more detailed block diagram of the gating
`sion transmitter cannot be used.
`40 generator of FIG. 3;
`FIGS. 5a and 5b show, respectively, the reference
`SUMMARY OF THE INVENTION
`pulse generator and corresponding waveforms;
`It is an object of the present invention to furnish an
`FIG. 6 shows the circuit diagram for the random
`encoding and decoding system and method which al-
`switching pulse generator of FIG. 3;
`lows use of a standard transmitter, require relatively lit-
`FIG. 7 is a more detailed block diagram showing the
`tle additional equipment and still have a high immunity 45 generation of the reset gate enable signals;
`to unauthorized decoding.
`FIG. 8 shows the circuits for the inverting and non-
`It is a further object of the‘ present invention to fur-
`inverting amplifiers of FIG. 3;
`nish a method and system for encoding and decoding
`FIG. 9 shovvs the circuit for the reset burst gate of
`the audio signal associated with the program to be
`FIG. 3;
`'
`‘
`transmitted, to prevent reception of said audio signal 50
`FIGS. 10a and 10b show, respectively, the spectrum
`without use of the decoding unit.
`usage and the encoding system for the audio portion of
`It is a further object of the present invention to pro-
`the signals;
`vide a Barker audio signal which is audible on a stan-
`FIG. 11 shows a decoder block diagram;
`,dard television signal without decoding, to give the in-
`FIG. 12 shows the circuits for the reference pulse and
`formation required by the subscriber to decide whether 55 burst separator of FIG. 11;
`or not to pay for the particular program.
`FIG. 13 shows the circuit for generating the reset and
`In accordance with the present invention, a standard
`decode triggers; and
`composite television signal having a video signal with a
`FIG. 14 shows the circuit for furnishing the enabling
`determined black level signifying picture black and fur-
`signals for the inverting and non-inverting amplifiers of
`ther having synchronizing signals of a determined syn- 60 the decoder.
`V
`chromzmg level and polarity relative to said black level
`DESCRIPTION OF THE PREFERRED I
`IS encoded by the followmg steps.
`EMBODIMENTS
`First, a sequence of reference pulses having a polarity
`opposite to said synchronizing polarity, each displaced 65
`by a determined time interval from a corresponding
`one of said synchronizing signals is generated. Said se—
`quence of reference pulses is combined with said com-
`posite television signal. The resulting signal, including
`
`A preferred embodiment of the present invention will
`now be described with reference to the drawing.
`The underlying principle of the present invention is
`best understood with reference to FIG. 1 which shows
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`the wave forms of both the standard television signal on
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`Apple v. PMC
`|PR2016-01520
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`chronization pulses. A standard transmitter can thus be
`used without modification.
`FIG. 2 shows the vertical blanking interval of the
`standard television signal after encoding.
`It will be
`noted that it
`is a standard vertical blanking interval
`with the vertical synchronizing pulses and equalizing
`pulses intact. The only difference is that the reference
`pulses have been added on the front porch of the hori-
`zontal sync pulses. Further it will be noted that decod-
`ing bursts have been added following the equalizing
`pulses. It is the function of these decoding bursts to in-
`dicate the polarity of the video signal for the subse-
`quent field, that is whether the subsequent field will
`have a black positive or a black negative level. Further
`it will be noted that just prior to the first equalizing
`pulses reset bursts are added. As will be described in
`more detail below, it is the function of the reset burst to
`reset the gate which determines the polarity of the sub-
`sequent frame. The use of these reset bursts allows a
`minimum equipment to be used in the decoders. Of
`course this is particularly desirable since there is a far
`larger number of decoders required than the signal en-
`co‘der at the transmitter. In the simplet possible em-
`bodiment of the present invention it is of course possi-
`ble to use a single decoding burst to indicate that the
`subsequent frame will be black positive, for example,
`and to Use the absence of decoding bursts to indicate a
`black negative frame. This type of system, although-
`simplest, offers the least security. In order to achieve
`greater security the decoding bursts may contain bursts
`of a number of frequencies and as many as eight bursts
`may be used. Thus a great flexibility in encoding to sig-
`nify the polarity of the next frame is available.
`The block diagram of the video encoder is shown in
`FIG. 3. A standard composite television signal (black
`negative) is furnished at input terminal 10. All parts of
`the signal received at
`terminal 10 'are transmitted
`through the non-inverting amplifier 11 except that the
`video portion of those fields for which the video por-
`tion is to be inverted is transmitted through inverting
`amplifier 12. Since the incoming standard composite
`television signal is simultaneously applied to the input
`of both amplifier 11 and amplifier 12, it is obvious that.
`gating signals will have to be provided to switch one
`amplifier on and one amplifier off at all times. The only
`exception is that with particular techniques used in the »
`present invention both amplifiers are cut off (furnish-
`ing Bi” voltage) for forming of the reference pulse. This
`furnishes an extremely reliable reference.
`The required enabling signals are furnished by gating 1
`generator 15, specifically, the signal on line A» enables
`amplifier 11, while the signal on line B enables ampli-
`fier 12. The gating generator in turn is controlled by the
`horizontal and vertical synchronization signals derived
`from the incoming composite television signal by
`means of a standard sync separator 13. The output of
`the sync separator is also used to sample the output of
`a random switching pulse generator whose so-sampled
`output is used to determine whether or not the ‘video
`portion of the subsequent field is to be inverted, that is
`whether or not the signal on line B is to appearduring
`the subsequent field. The sync separator 13 is a stan-
`dard circuit which may for example be found in FIG. 4
`in “Television Service Manual” 3rd Edition, second
`printing, 1970, published by Theodore Audel & Co.
`The circuits associated with units 14 and 15 will be dis-
`cussed in detail below. For the present it is sufficient
`that an e'ncoded video signal is derived at the combined
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`3
`which the encoder of the present invention operates
`and the signals following the encoding. Reference to
`line A shows a standard television signal having a black
`negative level and negative synchronization pulses. In
`particular, line A shows the interval between two se-
`quential horizontal synchronization pulses. The hori-
`zontal synchronization pulses are labelled respectively
`H1 and H2. On the back porch of the horizontal syn-
`chronization pulses are the color bursts which form
`part of the standard color television signal. Following
`the color bursts is the video portion of the signal. This
`is indicated in stylized form, that is a white, grey and
`black level as shown. Of course the actual video signal
`would have variations between these various levels de-
`pending upon the picture to be transmitted. In accor-
`dance with the present invention, the above-described
`signal is encoded in two ways; first a reference pulse is
`added on the front porch of the horizontal synchroniz-
`ing signals and the signal is transmitted in such a man-
`ner that the reference pulse occupies the amplitude lev-
`els and has the polarity normally associated with the
`synchronization signal. Although the horizontal and
`vertical synchronization signals are transmitted, these
`are transmitted at opposite polarity to their usual polar-
`ity, thereby preventing a receiver receiving such an en-
`coded'signal from synchronizing thereto. Further, the
`width of the reference pulses is made sufficiently nar-
`row that the synchronizing circuits of the receiver do
`not respond thereto. Thus the receiver receiving such
`an encoded signal will see an image which is unsyn-
`chronized both horizontally arid vertically, unless the
`decoder is activated by the subscriber.
`As an additional measure, the video portion of the
`signal indicated by the white, grey and black levels in
`the standard signal described above is inverted during
`some fields. The signal is either transmitted in the stan-
`dard black negative or in a black positive fashion
`throughout any one particular field, but the video sense
`may be reversed either from field to field, or else ran-
`domly as will be described below. Thus not only is the
`received signal, if not decoded, unsynchronized, but
`also the video levels are inverted. On a normal black
`and white television receiver a substantially blank re-
`sister will result. On a color receiver the luminance por-
`tion of the signal would at least partially cancel out.
`Since on opposite polarity fields, the chrominance sig—
`nal will be 180° out of phase while the sense of the
`color burst remains unchanged, the colors visible will
`have no discernible relation to the true information and
`will flicker strongly according to the random switching
`rate. Further the lack of horizontal synchronization will
`also cause the color burst gate to be unsynchronized
`with the color burst and on most receivers no color
`would be visible.
`Line B of FIG. 1 shows the encoded signal including
`the reference pulse. In this case the video portion of the
`signal has not been inverted and the black negative
`level still exists. In the following line, line C, the en-
`coded signal with reference pulse, and sync negative,
`black positive level is shown.
`Line D of FIG. 1 shows the RF envelope and indi-
`cates that the reference pulse represents peak power
`from the transmitter. It should be noted with reference
`to this Figure that the video transmitter sees a standard
`composite television signal except for the absence of
`the front porch of the horizontal synchronization
`pulses. The transmitter clamps at the pulse tip of the
`reference pulse instead of at the pulse tip of the syn-
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`Apple v. PMC
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`3,924,059
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`5
`outputs of amplifiers 11 and 12. It is further of course
`necessary that the reset bursts be added to the encoded
`signal. This is accomplished by enabling reset burst
`gate 16 via an output D of gating generator 15 at the
`time of the two horizontal line intervals immediately
`preceding the equalizing pulses in the vertical blanking
`interval (see also FIG. 2). It is further essential that the
`decoding burst indicated as following the equalizing
`pulses during the vertical blanking interval (again see
`FIG. 2) be added to the encoded video signal. This is
`accomplished by enabling either black negative burst
`gate 17 or black positive burst gate 18 via lines E and
`C, respectively. Of course, as mentioned above, in the
`simplest case one of gates 17 and 18 may be eliminated
`entirely and a single gate may be enabled to indicate a
`selected video polarity. In the Figure a plurality of burst
`frequency generators, namely generators 19a through
`19d are shown. Further shown is a burst frequency se-
`lector 20 which may comprise manually set switches
`interconnecting the burst frequency generators with
`one of the gates 16, 17 or 18. The selected bursts are
`then applied to the encoded video signal whenever a
`particular gate is enabled as discussed above. It should
`further be noted that gates 16, 17 and 18 must be fol-
`lowed by a stage having a high output impedance prior
`to connection to the video throughline 21 carrying the
`encoded video signals, to prevent excessive loading of
`this line. Burst frequency generators 19a through 19d
`are standard oscillators furnishing frequencies of be-
`tween 0.2 and 2 MHZ. A suitable circuit for one of the
`burst gates 16 through 18 and including a suitable cir-
`cuit to effect the high output impedance mentioned
`above is shown in FIG. 9 and will be discussed in detail
`following the description of said Figure.
`A more detailed diagram of the gating generator 15
`of FIG. 3 is shown in FIG. 4. It should be noted with ref-
`erence this Figure and all other block diagrams of this
`application, that a 1 output and a 0 output of a flip-flop
`refer to the states wherein the so-labelled outputs are
`enabled.
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`
`
`6
`the particular lines immediately preceding the black
`positive field, and at such times as do not include the
`reference pulse and horizontal blanking pulse. The tim-
`ing for activating line C of FIG. 3 is indicated as coming
`from terminal Z of counter 100. This is a schematic in-
`
`dication signifying a timing corresponding to the lines
`for which the coding bursts are required. In theory and
`in the simplest case it could of course be only a single
`line during the vertical blanking interval. Of course, if
`the output of the coding flip-flop 142 had beenla 0 the
`inverting burst pulse gate enable signal B would have
`been generated instead of the signal C. Signal E would
`be generated through AND gate 144. AND gate 144
`furnishes signal 13 in response to a 0 output of flip-flop
`142 occurring simultaneously with signal Z.
`A 1 output of flip—flop 142 occurring simultaneously
`with a signal from terminal W of counter 100 causes an
`output to appear at the output of AND gate 145~which
`in turn sets a polarity of flip—flop 146. The signal on line
`W is a signal signifying the line before the video portion
`of the subsequent field. It will be noted that both the
`coding flip-flop 142 and polarity flip-flop 146 are reset
`by a signal appearing at terminal Y of counter 100. This
`terminal schematically indicates the time for the reset
`pulse gate enable signal D of 'FIG. 3. It will be seen that
`this occurs during the two lines immediately preceding
`the equalizing pulses in the vertical blanking interval.
`Again the reset pulses are timed to avoid interference
`with either the reference pulse, the horizontal synchro-
`nizing pulse. or the color burst. Since the resetting of
`the flip-flop is accomplished by the first of these pulses,
`the second of course will be ineffective and is used for
`
`reliability only. It will be noted that polarity flip-flop
`146 has a 1 output only when the coding flip-flop indi-
`cated that the video polarity of the next field is to be in—
`verted and for a time period extending from the time
`that the flip-flop is set, namely from the timing of out-
`put W of counter 100, to the timing of output Y of
`counter 100. In other words, the whole vertical blank-
`ing interval is excluded as having a possible 1 output of
`flip-flop 146. Actually, reference to FIG. 2 will show
`that the output of 'flip-flop 146 ceases just prior to the
`beginning of the blanking interval, that is the last two
`lines of the preceding field are also excluded. Thus sig-
`nal B which appears at the output of AND gate 147,
`one of whose inputs is the 1 output of flip-flop 146, can
`exist only in portions of the signal not including the ver-
`tical blanking interval. It is of course further also re-
`quired to eliminate signal B during the times of the ref-
`erence pulse and: of the horizontal blanking interval.
`This is accomplished by taking the output of reference
`pulse generator 148, inverting it in inverter 149, and
`combining it in an OR gate 150 with the otuput of hori-
`zontal blanking generator 151, after inversion of said
`output by inverter 152. The output signal of OR gate
`150 constitutes the second input of AND gate 147. It is
`thus seen that signal B will appear only for a 1 output of
`coding flip-flop 142 and only for that portion of the
`composite video signal which carries the actual video
`information. The synchronizing intervals will always
`pass through non inverting amplifier 11, since amplifier
`12 will never be activated at times corresponding to
`said signals.
`At any time that signal B is not available, signal A
`must of course be available except during the reference
`pulse, which, in accordance with a preferred embodi-
`ment of the present invention, is inserted into the tele-
`vision signal by cutoff of the amplifiers (1 l or 12) pass-
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`PMC Exhibit 215
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`Apple v. PMC
`|PR201 6-01520
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`FIG. 4 shows a counter, 100, to whose count and
`reset inputs are, respectively, applied the horizontal
`and vertical synchronizing pulses derived from sync
`separators 13 of FIG. 3. This counter is an 8-bit counter
`and from it may be derived signals signifying particular
`lines in a given field. The random switching pulse gen-
`erator 14 of FIG. 3 is shown embodied in a random
`noise generator 140 whose output comprises both posi-
`tive and negative signals appearing randomly with re-
`spect to time. The output of random noise generator
`140 is sampled by a sampling gate 141. When a counter
`output furnishes a signal corresponding to the line be—
`fore the coding bursts, a switch 141 is closed to sample
`the state of the random noise generator. If the output of
`random noise generator 140 is a positive output, this
`will cause a setting of coding flip—flop 142 i.e., the 1
`output is enabled. 1 Output of coding flip-flop 142 sig-
`nifies that the video portion of the subsequent field is to
`be inverted. Thus it is necessary to enable inverting am-
`plifier 12 during the video portion of the subsequent
`field; although non-inverting amplifier 1 1 must be acti-
`vated during the horizontal blanking interval as well as
`the vertical blanking interval even during fields having
`an inverted video signal. Further it is necessary to insert
`the appropriate coding bursts, that is to enable black
`positive burst gate 18 at the correct times during the
`vertical blanking interval (see FIG. 2). Thus signal C
`(the enable signal for gate 18) must be furnished during
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`particular line in a field, but that the timing is correct to
`prevent interference with the reference pulse, the hori-
`zontal synchronizing pulse, and the color burst. The
`counter, as is well known, is a binary counter using a
`plurality of flip-flops. Any particular count can be de-
`termined by the correct combination of the outputs of
`various ones of these flip-flops. Reference to FIG. 7
`shows that selected ones of the flip-flops have an out-
`put which is combined in an AND circuit 400. The out—
`put of AND circuit 400 is combined in a second AND
`circuit 401 with the inverted blanking and reference
`pulse generator outputs, derived from reference pulse
`generator 402 and blanking generator 404. The output
`of AND gate 401 then constitutes signal Y at the output
`of counter 100 which, again, is equivalent to signal D of
`FIG. 3. The timing for the polarity burst gate enable
`signal, signal Z, is derived in exactly the same fashion as
`described above. No further discussion is therefore
`necessary.
`‘
`The gating signals A and B developed as shown in
`FIG. 4 are then applied to enable the non-inverting and
`inverting amplifiers 11 and 12 respectively.
`(FIG. 8 shows the inverting and non-inverting amplifi-
`ers. The inverting amplifier comprises a transistor 500
`and a transistor 501 which together constitute a differ-
`ential amplifier. Specifically, the collector of transistor
`500 is connected to the positive supply line via a resis-
`tance 502, while the collector of transistor 501 is di-
`rectly connected to said positive supply line. The emit-
`ter of transistor 500 is connected to the emitter of tran-
`sistor 501 by a resistance 503, which determines the
`gain of the differential amplifier. The emitter of transis-
`tor 501 is connected to ground potential via a resistor
`505 whose resistance is substantially higher than the
`resistance of resistor 503. The output of the amplifier is
`derived from the collector of transistor 800. Further, a
`transistor 508 has an emitter-collector circuit con-
`nected from the ungrounded terminal of resistance 510
`to the positive supply line.
`The non—inverting amplifier is also a differential am-
`plifier. This differential amplifier comprises transistors
`504 and 506 whose emitters are interconnected by a
`resistance 507. The collector of transistor 504 is di-
`rectly connected to the positive supply line, while the
`collector of transistor 506 is connected in common
`with the collector of transistor 500. This common con-
`nection constitutes the output furnishing the encoded
`television signal. Also, transistor 509 has its emitter-
`collector circuit connected from the ungrounded ter-
`minal of resistance 807ato the positive supply line.
`Gating signal B is applied to the base of the transistor
`508, while gating signal A is applied to the base of tran-
`sistor 509.
`The circuit operates as follows:
`The uncncoded television signal is applied simulta-
`neously to the bases of both transistor 500 and transis-
`tor 504. In the presence of an enable signal B at the
`base of transistor 508, this transistor is blocked allow-
`ing the differential amplifier comprising transistors 500
`and 501 to operate normally. In the absence of such en-
`able signal,