CA1123950A - Television security system - Google Patents
Television security systemInfo
- Publication number
- CA1123950A CA1123950A CA280,865A CA280865A CA1123950A CA 1123950 A CA1123950 A CA 1123950A CA 280865 A CA280865 A CA 280865A CA 1123950 A CA1123950 A CA 1123950A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- television
- carrier
- scramble
- frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K3/00—Jamming of communication; Counter-measures
- H04K3/80—Jamming or countermeasure characterized by its function
- H04K3/82—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection
- H04K3/825—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection by jamming
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K3/00—Jamming of communication; Counter-measures
- H04K3/40—Jamming having variable characteristics
- H04K3/42—Jamming having variable characteristics characterized by the control of the jamming frequency or wavelength
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/166—Passage/non-passage of the television signal, e.g. jamming, band suppression
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K2203/00—Jamming of communication; Countermeasures
- H04K2203/10—Jamming or countermeasure used for a particular application
- H04K2203/14—Jamming or countermeasure used for a particular application for the transfer of light or images, e.g. for video-surveillance, for television or from a computer screen
Abstract
S P E C I F I C A T I O N
TELEVISION SECURITY SYSTEM
ABSTRACT
A system for subscription TV security which is comprised of a scramble signal generator which adds a modulated RF
carrier signal to the TV channel transmission. Preferably the frequency of the scramble signal generator is selected to fall within the band of frequencies of the TV channel between the video carrier and the audio carrier. The TV channel is transmitted to receivers encoded with the scramble signal carrier providing false and misleading information, preventing the receiver from reconstituting a coherent picture or sound while this scramble signal is present. The transmitted signal is decoded, (i.e. scramble signal removed), restoring regular reception by filtering with a sharply tuned high-Q notch filter attached to the drop line going to a TV receiver. By careful selection of the band width and attenuation of the filter and pre-emphasis of the channel band, degradation of the video information is prevented.
TELEVISION SECURITY SYSTEM
ABSTRACT
A system for subscription TV security which is comprised of a scramble signal generator which adds a modulated RF
carrier signal to the TV channel transmission. Preferably the frequency of the scramble signal generator is selected to fall within the band of frequencies of the TV channel between the video carrier and the audio carrier. The TV channel is transmitted to receivers encoded with the scramble signal carrier providing false and misleading information, preventing the receiver from reconstituting a coherent picture or sound while this scramble signal is present. The transmitted signal is decoded, (i.e. scramble signal removed), restoring regular reception by filtering with a sharply tuned high-Q notch filter attached to the drop line going to a TV receiver. By careful selection of the band width and attenuation of the filter and pre-emphasis of the channel band, degradation of the video information is prevented.
Description
~Z395~
This system relates -to television jamming systems and more particularly rela-tes to systems for encoding and decoding television transmissions for subscrip-tion TV.
The need for practical systems offering security for pay TV has become increasingly apparent. Both active and passive systems have been developed and are marketed at present which are designed to prevent non-subscribers from watching pay TV premium channels. Some of the accepted systems include trapping at the pole, converters, switchable taps, and various -~
encodiny-decoding systems. In general, the cost of these systems is directly proportional to the degree of security they offer.
It seems fair to say, however, that there is no fully secure system and the present systems have not achieved wide acceptance.
Still, it remains necessary to secure pay TV transmissions to some extent in order to make pay TV a realistic business proposition.
The purpose of the present invention is to provide a system which can provide security for a subscription TV efficiently and economicall~.
The present invention comprises adding a scramble signal carrier to the TV channel band somewhere between the - video carrier and khe audio carrier which is controlled in amplitude, ~requency, and modulation to render TV reception unintelligible. This signal is added to the TV transmission preferably at the point of origin or the head end o~ a C~TV
installation. When the TV -transmission is received at a TV
set, the receiver is unable to reconstitute a coherent picture or sound. With the addition of a decoder or descrambler in the form of a sharply tuned LC notch filter the scramble signal ma~ be removed before processing, restoring a TV receiver to regular reception.
LZ39S~
The sys-tem of the present invention offers a novel solution to the problem of pay TV security. Its theoretical foundation is clear and concise, its implementation is ideally suited to high technology mass production, resulting in low cost to the user~ The system is universally applicable, i.e~
it will functio~ not only in CATV, but in MDS (Multipoint Distribution System) and over the air systems as well.
It is one object of -the present invention to provide a system for securing a TV channel transmission for reception by only those who subscribe to the system.
Another object of the present invention is to provide a TV channel encoding security system which is relatively simple in design.
Yet another object of the present invention is to provide a TV encoding security system which has high reliability and serviceability.
Still another object of the present invention is to provide a TV channel encoding security system with a carefully controlled scram~le signal or signals.
Still another object of the present invention is to provide a TV encoding security system which minimizes the effects of decoding by pre-emphasizing the video information.
Other objects, advantages and novel features of the invention will become apparent Erom the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein li]~e reference numbers identify like parts throughout.
IN TEIE DRAWINGS
Figure la is a graphical illustration of a typical TV channel frequency spectrum with a scrambling signal carrier added;
~LiL;~3~S~
Figure lb is a graphical illustra-tion of a typical TV channel frequency spectrum with the scrambling sicJnal removed;
Figure 2 is a block diagram of a typical CATV system equipped with the encoder;
Figure 3 is a graphical illustration of a typical TV
channel frequency spectrum with the scrambling signal carrier added approximately mid-way between the video and audio carriers;
Figure 4 is a schematic block diagram illustrating the encoder or scramble signal generator and its connection to a TV channel processing system;
Figure 5 is a graphical illustration showing the typical frequency response of an amplifier for pre-emphasizing the video information in a TV channel;
: Figure 6 is a graphical illustration of a typical TV channel frequency spectrum with the scrambling signal and the pre-emphasized portion of the transmitted RF band;
Figure 7 is a graphical illustration showing the typical frequency response of the decoder, and, .' 20 Figure 7b is a graphical illustration showing the . frequency response of a sharply tuned LC notch filter decoder aftex the frequency response of a pre-emphasizing amplifier has been superimposed on it.
; It is well known that a TV receiver will detect as video inEormation the presence of a single frequency sinusoidal signal, located between the visual and aural carriers of a TV
channel. When such a signal is not part of the regular picture material, it will be observed as interference, or disturbance of the intended picture.
The degree of disturbance by this interference signal r~
3~5~;3 primarily depends on the combination of:
1. The level of the signal relative to -the visual and aural carriers.
This system relates -to television jamming systems and more particularly rela-tes to systems for encoding and decoding television transmissions for subscrip-tion TV.
The need for practical systems offering security for pay TV has become increasingly apparent. Both active and passive systems have been developed and are marketed at present which are designed to prevent non-subscribers from watching pay TV premium channels. Some of the accepted systems include trapping at the pole, converters, switchable taps, and various -~
encodiny-decoding systems. In general, the cost of these systems is directly proportional to the degree of security they offer.
It seems fair to say, however, that there is no fully secure system and the present systems have not achieved wide acceptance.
Still, it remains necessary to secure pay TV transmissions to some extent in order to make pay TV a realistic business proposition.
The purpose of the present invention is to provide a system which can provide security for a subscription TV efficiently and economicall~.
The present invention comprises adding a scramble signal carrier to the TV channel band somewhere between the - video carrier and khe audio carrier which is controlled in amplitude, ~requency, and modulation to render TV reception unintelligible. This signal is added to the TV transmission preferably at the point of origin or the head end o~ a C~TV
installation. When the TV -transmission is received at a TV
set, the receiver is unable to reconstitute a coherent picture or sound. With the addition of a decoder or descrambler in the form of a sharply tuned LC notch filter the scramble signal ma~ be removed before processing, restoring a TV receiver to regular reception.
LZ39S~
The sys-tem of the present invention offers a novel solution to the problem of pay TV security. Its theoretical foundation is clear and concise, its implementation is ideally suited to high technology mass production, resulting in low cost to the user~ The system is universally applicable, i.e~
it will functio~ not only in CATV, but in MDS (Multipoint Distribution System) and over the air systems as well.
It is one object of -the present invention to provide a system for securing a TV channel transmission for reception by only those who subscribe to the system.
Another object of the present invention is to provide a TV channel encoding security system which is relatively simple in design.
Yet another object of the present invention is to provide a TV encoding security system which has high reliability and serviceability.
Still another object of the present invention is to provide a TV channel encoding security system with a carefully controlled scram~le signal or signals.
Still another object of the present invention is to provide a TV encoding security system which minimizes the effects of decoding by pre-emphasizing the video information.
Other objects, advantages and novel features of the invention will become apparent Erom the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein li]~e reference numbers identify like parts throughout.
IN TEIE DRAWINGS
Figure la is a graphical illustration of a typical TV channel frequency spectrum with a scrambling signal carrier added;
~LiL;~3~S~
Figure lb is a graphical illustra-tion of a typical TV channel frequency spectrum with the scrambling sicJnal removed;
Figure 2 is a block diagram of a typical CATV system equipped with the encoder;
Figure 3 is a graphical illustration of a typical TV
channel frequency spectrum with the scrambling signal carrier added approximately mid-way between the video and audio carriers;
Figure 4 is a schematic block diagram illustrating the encoder or scramble signal generator and its connection to a TV channel processing system;
Figure 5 is a graphical illustration showing the typical frequency response of an amplifier for pre-emphasizing the video information in a TV channel;
: Figure 6 is a graphical illustration of a typical TV channel frequency spectrum with the scrambling signal and the pre-emphasized portion of the transmitted RF band;
Figure 7 is a graphical illustration showing the typical frequency response of the decoder, and, .' 20 Figure 7b is a graphical illustration showing the . frequency response of a sharply tuned LC notch filter decoder aftex the frequency response of a pre-emphasizing amplifier has been superimposed on it.
; It is well known that a TV receiver will detect as video inEormation the presence of a single frequency sinusoidal signal, located between the visual and aural carriers of a TV
channel. When such a signal is not part of the regular picture material, it will be observed as interference, or disturbance of the intended picture.
The degree of disturbance by this interference signal r~
3~5~;3 primarily depends on the combination of:
1. The level of the signal relative to -the visual and aural carriers.
2. Frequency of the interfering signal, i.e. the position of this signal in the frequency domain relative to the visual and aural carriers.
3. Modulation of the interfering signal.
The threshold of in-terference by the interfering or scrambling signal is a strong function of the signaI's frequency and modulation. Considerlng a pure sinusoidal RF scrambling signal, however, it was determined that the threshold of inter-ference is at the -45dB level with respect to the visual carrier, ~ when the scrambling signal is anywhere between the visual and ; aural carriers. The degree of interference by the scrambling signal becomes more severe with increasing level, and the picture is greatly impaired at the OdB level.
~ In general, for a given relative level of the scrambling ;~ signal, the picture quality becomes more objectionable as the scrambling signal is moved closer in frequency to the visual carrier. The sound quality is degraded in a similar fashion - when the scrambling signal is moved close in frequency to the aural carrier. There are also frequencies which are more effective in disrupting picture and sound reception than others;
e.g. if the scrambling signal is harmonically related to the line scanning frequency (lS.73~ K~lz) and/or the carrier fre-quencies, TV reception is of much poorer quality than if some other frequencies are chosen.
Modulation of the scrambling signal increases the level of interference with TV reception. AM modulation was found to be generally more effective than FM, and modulating ~ . :
~lZ39Sq~
frequencies below 100 Hz result in greater scrambling of the pic-ture material than if some other frequencies were used.
It can be seen frorn the preceding brief analysis that a proper choice of the encoding or scrambling signal, i.e.
one of a certain level, a selected frequency, and one which is AM modulated, will make enjoyable TV reception impossible.
Among the novel features incorporated in the system is the ability to inject and then remove an in-channel single frequency interference, such as an encoding signal, by means of a sharply tuned notch filter. If the notch filter, or decoder descrambler, attenuates the scrambling signal to approximately the -45 ds level, TV reception is acceptable in most cases. Figures la and lb depict schematically the ; frequency spectrum of a TV channel with a scrambling signal present between the video and audio carriers and with the scrambling signal removed respectively.
In Figures la and lb the frequency scale of 6 MHz indicates the band width allocation for each channel with the visual carrier at 1.25 MHz, the color subcarrier at ~.83 MHz and the aural carrier at 5.75 MHz above the lowest frequence of the band. In each of the graphical illustrations Figures 3, 5, 6, 7a and 7b the same rule wiLl apply, i.e. the frequency scale represents any channel bandwidth allocation of 6MHz.
In practice, it is not possible to remove a single frequency. The decoder or notch filter of the invention removes a narrow band of frequencies about the undesired signal. This means, of course, that a small amount of regular picture material is removed from the transmission along with the interfering signal~ Thus the in-channel notch filter or decoder, must be s-table, efficient and accurate.
" ~
,, ~L;239~
The principle of the system is the inser-tion of one or more scrambling or carrier signals, into a par-ticular TV
channel between the visual and audio carriers, thereby obliterating (i.e. interfering wi-th) the received picture and sound. The reception may be restored, descrambled, or more correctly decoded, for a subscriber by removing the Ealse and misleading scrambling signal(s) at the TV set.
The scrambling signal is generated by the encoder 12 which is located typically at the point of origin or at the head-end 10 of a CATV facility, as shown. The output of the head-end 10 with the scramble or encoding signal is delivered to distribution amplifiers 1~, 16 and then to TV receivers (not shown). All TV sets will receive normal reception except on the preselected channel which will be rendered unintelligible by the misleading information from the interfering carrier or ; encoding signal. Those who wish to enjoy the scrambled channel will subscribe and have a decoder or descrambler 18, which will be more fully described hereinafter, installed in their line.
Non-subscribers will be able to receive other channels normally, but may not vie~ the channel with the scrambled display.
If it is desired to scramble a channel for purposes of pay TV security, the preferred choice of parame-ters for the encoding signal which will render reception unenjoyable without the use of the clecoder llnit are as follows:
1. A frequency difference of 2.257 M~lz - lKlIz between the scrambling signal carrier and visual carrier.
2. A Odb relative level between the scrambling signa:L
carrier and the visual carrier.
3. A 15HzAM and lHzAM modulation of the scrambling signal carrier.
."'`1 ~Z3~5~
The threshold of in-terference by the interfering or scrambling signal is a strong function of the signaI's frequency and modulation. Considerlng a pure sinusoidal RF scrambling signal, however, it was determined that the threshold of inter-ference is at the -45dB level with respect to the visual carrier, ~ when the scrambling signal is anywhere between the visual and ; aural carriers. The degree of interference by the scrambling signal becomes more severe with increasing level, and the picture is greatly impaired at the OdB level.
~ In general, for a given relative level of the scrambling ;~ signal, the picture quality becomes more objectionable as the scrambling signal is moved closer in frequency to the visual carrier. The sound quality is degraded in a similar fashion - when the scrambling signal is moved close in frequency to the aural carrier. There are also frequencies which are more effective in disrupting picture and sound reception than others;
e.g. if the scrambling signal is harmonically related to the line scanning frequency (lS.73~ K~lz) and/or the carrier fre-quencies, TV reception is of much poorer quality than if some other frequencies are chosen.
Modulation of the scrambling signal increases the level of interference with TV reception. AM modulation was found to be generally more effective than FM, and modulating ~ . :
~lZ39Sq~
frequencies below 100 Hz result in greater scrambling of the pic-ture material than if some other frequencies were used.
It can be seen frorn the preceding brief analysis that a proper choice of the encoding or scrambling signal, i.e.
one of a certain level, a selected frequency, and one which is AM modulated, will make enjoyable TV reception impossible.
Among the novel features incorporated in the system is the ability to inject and then remove an in-channel single frequency interference, such as an encoding signal, by means of a sharply tuned notch filter. If the notch filter, or decoder descrambler, attenuates the scrambling signal to approximately the -45 ds level, TV reception is acceptable in most cases. Figures la and lb depict schematically the ; frequency spectrum of a TV channel with a scrambling signal present between the video and audio carriers and with the scrambling signal removed respectively.
In Figures la and lb the frequency scale of 6 MHz indicates the band width allocation for each channel with the visual carrier at 1.25 MHz, the color subcarrier at ~.83 MHz and the aural carrier at 5.75 MHz above the lowest frequence of the band. In each of the graphical illustrations Figures 3, 5, 6, 7a and 7b the same rule wiLl apply, i.e. the frequency scale represents any channel bandwidth allocation of 6MHz.
In practice, it is not possible to remove a single frequency. The decoder or notch filter of the invention removes a narrow band of frequencies about the undesired signal. This means, of course, that a small amount of regular picture material is removed from the transmission along with the interfering signal~ Thus the in-channel notch filter or decoder, must be s-table, efficient and accurate.
" ~
,, ~L;239~
The principle of the system is the inser-tion of one or more scrambling or carrier signals, into a par-ticular TV
channel between the visual and audio carriers, thereby obliterating (i.e. interfering wi-th) the received picture and sound. The reception may be restored, descrambled, or more correctly decoded, for a subscriber by removing the Ealse and misleading scrambling signal(s) at the TV set.
The scrambling signal is generated by the encoder 12 which is located typically at the point of origin or at the head-end 10 of a CATV facility, as shown. The output of the head-end 10 with the scramble or encoding signal is delivered to distribution amplifiers 1~, 16 and then to TV receivers (not shown). All TV sets will receive normal reception except on the preselected channel which will be rendered unintelligible by the misleading information from the interfering carrier or ; encoding signal. Those who wish to enjoy the scrambled channel will subscribe and have a decoder or descrambler 18, which will be more fully described hereinafter, installed in their line.
Non-subscribers will be able to receive other channels normally, but may not vie~ the channel with the scrambled display.
If it is desired to scramble a channel for purposes of pay TV security, the preferred choice of parame-ters for the encoding signal which will render reception unenjoyable without the use of the clecoder llnit are as follows:
1. A frequency difference of 2.257 M~lz - lKlIz between the scrambling signal carrier and visual carrier.
2. A Odb relative level between the scrambling signa:L
carrier and the visual carrier.
3. A 15HzAM and lHzAM modulation of the scrambling signal carrier.
."'`1 ~Z3~5~
4. An 80~ modulation of the scrambling RF signal.
It can be noted from this data tha-t the scrambling signal carrier is very nearly midway between the channel visual and audio carriers as shown in Figure 3.
Inves-tigation indicates that this choice of parameters is preferred and is one of several which will function well in the system. In this instance, the scrambl:ing signal provides false and misleading information to the television receiver and has the following effect on TV reception.
; 10 1. The 2.257 MHz signal is detected and amplified along with regular video information by the TV
set. Because of the 1 KHz AM modulation the inter-~erence appears as a set of horizontal bars across the receiver screen. The 15 Hz AM modulation interferes with the automatic gain control (AGC), color information, and vertical synchronizing pulses, thus causing the picture to roll and jump.
2. The beats and harmonics generated by the video detector beccme part of the 4.5 MHz sound ~-~ 20 information. The lKHz AM modulation, passing through the limiters, is detected and amplified by the audio circuits such that the 1 KHz tone ~rom the speakers overrides regular sound material.
Additionally r the lS Hz AM modulation is audible as a "chirping" sound.
I'his frequency of 2.257 MHz interleaves the scrambling signal between harmonics of the scanning frequency, which arrangement facilitates the eventual descrambling process.
This frequency difference of 2.257 MHz also positions the scrambling signal away from the chroma information, so that colors are not impaired after processing through the decoder.
~ .
'~'~ , ' . ' ~Z3~
Figure ~ is a block diagram of the encodlny unit 12 and the connections to other parts of a typical CATV head-end installation. The scrambl.e signal Erequency is generated by a erystal eontrolled rf oseillator 20 and modulated by oseil-lator 40. The erystal is maintained in an oven for added stability. ~ series of band pass fil-ters 22 reduee the harmonie eontent to -70 dB with respect to the fundamental. Another highly stable crystal oscillator 24, operating at 2.257 MHz, is used to produee a reference for the visual carrier. This 2.2S7 MHz signal is then combined i.n mixer 26 with the serambling signal from tap 32, and it is to this frequeney, i.eO the seramble signal frequency minus 2.257 MHz, that the visual carrier of ~: the channel is phase locked within signal processor 30 after ~; passing through filter 28. (Conneetion of band pass filter 28 to signal proeessor 30 for phase loeking is shown dotted beeause, though preferred, it is optional.) The phase loeking is preferred beeause it insures -~ that 'che 2.257 MHz frequeney differenee will remain eonstant for the system.
The pre-emphasizing amplifier 38 proeesses the rf band eontaining the ehannel in such a way as to eounterbalance most of the degradation antieipated from the deeoding proeess.
It amplifies the band symmetrically about the scramble signal frequeney point as shown at 42 of Figure 6. Figure 5 shows the frequeney response of the pre-emphasizing amplifier, providing approximately 12dB gain at the seramble signal frequeney.
The pre-emphasized ehannel band is then eombined wi-th the serambling signal and is eoupled into the eable system vla an impedanee matching device 36. The frequenc~ speetrum of the transmitted rf band with the serambling signal and pre-emphc~sis amplification is pictured in Figure 6.
'~,~
~LlZ~5~
The descramblincJ process consists of removiny the scrambling signal from the channel rf bancl. This is accomplished by connecting a descrambler unit 18 (Figure 2) into -the sub-scriber's drop line.
. ~
`~ As men-tioned before, the descrambler is a sharply tuned LC notch fil-ter also called a band elimination filter, whose frèquency spectrum is symmetric about the scrambling signal. It is a completely passive device requiring no po~7er for its operation. The ultimate attenuation of the descrambler 18 should be in excess of 60 dB at the scramble signal frequency, .::
the notch being sufficiently wide to remove the AM sidebands of the scrambling signal, but being sufficiently narrow to prevent serious degradation of the video information. Outside the notch, the decoder impedance should provide 75 Ohm impedance match and transmission attenuation less than l dB. A band width of 1.25 MHz at the 3 db level is preferred. Figure 7a shows the frequency response of the decoder, while ~igure 7b shows the frequency response of the pre-emphasizing amplifier superimposed on Figure 7a to counterbalance any deyradation caused by the decoder. It can be seen that the ultimate band width of the decoder 18 is chosen to be less than 0.75 MHz at the 3d~ point.
The frequency of the scramble signal is carefully selected not only to provide maximum interference but to provide a picture having maximum quality when it is removed. The frequency oE 2.25 MHz is a multiple of 60 Hz and could produce faint vertical lines in the picture if any of the interfering signal got through the descrambler 18. For this reason a sliyht offset is added to the 2.25 MHz frequency to make it closer to a multiple of the horizontal sweep frequency of 15.75 KHz.
Thus the final selected frequency of 2.257 (offset .007 MHz ,, _ g _ .
` '' ~; ' ~L~23~S~3 from 2.25 Mllz)has the addi-tional advantage of rendering the interfering signal horizon-tal or almos-t parallel with the horizontal lines of the picture. Thus any trace of the inter-fering signal not comple-tely removed by the descrambler is rendered invisible to the naked eye.
It should be apparent from the preceding discussion that the sole modification of the TV channel is the addition oE what amounts to another carrier signal. This third carrier, ; the scrambling signal does not, however, interact with the rest of the rf information in the channel, because the scrambling signal is co~lbined with the regular transmission through a linear network. The actual "scrambling" is accomplished by the receiver, which is unable to reconstitute a coherent TV
picture while the scrambling signal is present. The scrambling signal, located as it is in the TV channel is readily processed by the line amplifiers of a cable system. It should be noted that the system of encoding and decoding described herein may be applied to other communication systems in general and is not necessarily limited to television channels. The degree of security provided by the system of this invention is more than adequate for most subscriber TV operations.
; Having described what is believed to be the best mode by which the invention may be performed, it will be seen that the invention may be particularly defined as follows:
A television security system comprising processing means for processing a television signal having a v:ideo carrier and audio carrier, scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers oE said television signal such that said television signal is scrambled thereby, said at least one ~Z3~9~0 scrambliny signal having a Erequency substantially in the range of one-fourth to three-Eourths of the frequency in-terval between the video carrier and the audio carrier, -transmitting means for transmitting said scrambled television signal to television receivers, and filter means for fil-tering out said at ]east one scramble signal from said -television receiver circuits.
~- The invention further comprises a method of securing a television channel transmission comprising processing a television signal having a video carrier and an audio carrier, generating at least one scramble signal at a frequency substan tially in the range of one-fourth to -three-fourths of the frequency interval between the video and audio carriers of the television signal, combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby, transmitting said scrambled television signal to a plurality of television receivers, and filtering ou-t said scramble signal from said scrambled television signal at the input to the television receivers.
Obviously many modifications and variations of the invention are possible in the light of the above teachings.
It is therefore -to be understood that the full scope of the invention is not limited to the details disclosed herein and may be practiced otherwise than as speciEically described herein.
~,`
It can be noted from this data tha-t the scrambling signal carrier is very nearly midway between the channel visual and audio carriers as shown in Figure 3.
Inves-tigation indicates that this choice of parameters is preferred and is one of several which will function well in the system. In this instance, the scrambl:ing signal provides false and misleading information to the television receiver and has the following effect on TV reception.
; 10 1. The 2.257 MHz signal is detected and amplified along with regular video information by the TV
set. Because of the 1 KHz AM modulation the inter-~erence appears as a set of horizontal bars across the receiver screen. The 15 Hz AM modulation interferes with the automatic gain control (AGC), color information, and vertical synchronizing pulses, thus causing the picture to roll and jump.
2. The beats and harmonics generated by the video detector beccme part of the 4.5 MHz sound ~-~ 20 information. The lKHz AM modulation, passing through the limiters, is detected and amplified by the audio circuits such that the 1 KHz tone ~rom the speakers overrides regular sound material.
Additionally r the lS Hz AM modulation is audible as a "chirping" sound.
I'his frequency of 2.257 MHz interleaves the scrambling signal between harmonics of the scanning frequency, which arrangement facilitates the eventual descrambling process.
This frequency difference of 2.257 MHz also positions the scrambling signal away from the chroma information, so that colors are not impaired after processing through the decoder.
~ .
'~'~ , ' . ' ~Z3~
Figure ~ is a block diagram of the encodlny unit 12 and the connections to other parts of a typical CATV head-end installation. The scrambl.e signal Erequency is generated by a erystal eontrolled rf oseillator 20 and modulated by oseil-lator 40. The erystal is maintained in an oven for added stability. ~ series of band pass fil-ters 22 reduee the harmonie eontent to -70 dB with respect to the fundamental. Another highly stable crystal oscillator 24, operating at 2.257 MHz, is used to produee a reference for the visual carrier. This 2.2S7 MHz signal is then combined i.n mixer 26 with the serambling signal from tap 32, and it is to this frequeney, i.eO the seramble signal frequency minus 2.257 MHz, that the visual carrier of ~: the channel is phase locked within signal processor 30 after ~; passing through filter 28. (Conneetion of band pass filter 28 to signal proeessor 30 for phase loeking is shown dotted beeause, though preferred, it is optional.) The phase loeking is preferred beeause it insures -~ that 'che 2.257 MHz frequeney differenee will remain eonstant for the system.
The pre-emphasizing amplifier 38 proeesses the rf band eontaining the ehannel in such a way as to eounterbalance most of the degradation antieipated from the deeoding proeess.
It amplifies the band symmetrically about the scramble signal frequeney point as shown at 42 of Figure 6. Figure 5 shows the frequeney response of the pre-emphasizing amplifier, providing approximately 12dB gain at the seramble signal frequeney.
The pre-emphasized ehannel band is then eombined wi-th the serambling signal and is eoupled into the eable system vla an impedanee matching device 36. The frequenc~ speetrum of the transmitted rf band with the serambling signal and pre-emphc~sis amplification is pictured in Figure 6.
'~,~
~LlZ~5~
The descramblincJ process consists of removiny the scrambling signal from the channel rf bancl. This is accomplished by connecting a descrambler unit 18 (Figure 2) into -the sub-scriber's drop line.
. ~
`~ As men-tioned before, the descrambler is a sharply tuned LC notch fil-ter also called a band elimination filter, whose frèquency spectrum is symmetric about the scrambling signal. It is a completely passive device requiring no po~7er for its operation. The ultimate attenuation of the descrambler 18 should be in excess of 60 dB at the scramble signal frequency, .::
the notch being sufficiently wide to remove the AM sidebands of the scrambling signal, but being sufficiently narrow to prevent serious degradation of the video information. Outside the notch, the decoder impedance should provide 75 Ohm impedance match and transmission attenuation less than l dB. A band width of 1.25 MHz at the 3 db level is preferred. Figure 7a shows the frequency response of the decoder, while ~igure 7b shows the frequency response of the pre-emphasizing amplifier superimposed on Figure 7a to counterbalance any deyradation caused by the decoder. It can be seen that the ultimate band width of the decoder 18 is chosen to be less than 0.75 MHz at the 3d~ point.
The frequency of the scramble signal is carefully selected not only to provide maximum interference but to provide a picture having maximum quality when it is removed. The frequency oE 2.25 MHz is a multiple of 60 Hz and could produce faint vertical lines in the picture if any of the interfering signal got through the descrambler 18. For this reason a sliyht offset is added to the 2.25 MHz frequency to make it closer to a multiple of the horizontal sweep frequency of 15.75 KHz.
Thus the final selected frequency of 2.257 (offset .007 MHz ,, _ g _ .
` '' ~; ' ~L~23~S~3 from 2.25 Mllz)has the addi-tional advantage of rendering the interfering signal horizon-tal or almos-t parallel with the horizontal lines of the picture. Thus any trace of the inter-fering signal not comple-tely removed by the descrambler is rendered invisible to the naked eye.
It should be apparent from the preceding discussion that the sole modification of the TV channel is the addition oE what amounts to another carrier signal. This third carrier, ; the scrambling signal does not, however, interact with the rest of the rf information in the channel, because the scrambling signal is co~lbined with the regular transmission through a linear network. The actual "scrambling" is accomplished by the receiver, which is unable to reconstitute a coherent TV
picture while the scrambling signal is present. The scrambling signal, located as it is in the TV channel is readily processed by the line amplifiers of a cable system. It should be noted that the system of encoding and decoding described herein may be applied to other communication systems in general and is not necessarily limited to television channels. The degree of security provided by the system of this invention is more than adequate for most subscriber TV operations.
; Having described what is believed to be the best mode by which the invention may be performed, it will be seen that the invention may be particularly defined as follows:
A television security system comprising processing means for processing a television signal having a v:ideo carrier and audio carrier, scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers oE said television signal such that said television signal is scrambled thereby, said at least one ~Z3~9~0 scrambliny signal having a Erequency substantially in the range of one-fourth to three-Eourths of the frequency in-terval between the video carrier and the audio carrier, -transmitting means for transmitting said scrambled television signal to television receivers, and filter means for fil-tering out said at ]east one scramble signal from said -television receiver circuits.
~- The invention further comprises a method of securing a television channel transmission comprising processing a television signal having a video carrier and an audio carrier, generating at least one scramble signal at a frequency substan tially in the range of one-fourth to -three-fourths of the frequency interval between the video and audio carriers of the television signal, combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby, transmitting said scrambled television signal to a plurality of television receivers, and filtering ou-t said scramble signal from said scrambled television signal at the input to the television receivers.
Obviously many modifications and variations of the invention are possible in the light of the above teachings.
It is therefore -to be understood that the full scope of the invention is not limited to the details disclosed herein and may be practiced otherwise than as speciEically described herein.
~,`
Claims (45)
1. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits.
2. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency.
3. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal sucn that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits; and modulating means for modulating said at least one scramble signal at substantially 15 Hz and 1 KHz.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal sucn that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits; and modulating means for modulating said at least one scramble signal at substantially 15 Hz and 1 KHz.
4. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein the amplitude or said at least one scramble signal is at 0 db relative to the video carrier of said television signal.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein the amplitude or said at least one scramble signal is at 0 db relative to the video carrier of said television signal.
5. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal sucn that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits; and phase-locking means for phase locking the at least one said scramble signal relative to said video carrier signal.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal sucn that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits; and phase-locking means for phase locking the at least one said scramble signal relative to said video carrier signal.
6. A television security system comprising;
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers; filter means for filtering out said at least one scramble signal from said television receiver circuits;
phase-locking means for phase locking the at least one said scramble signal relative to said video carrier signal;
said phase locking means comprising:
mixer means for mixing said at least one scramble signal with a signal equal to the difference between said video carrier signal and said at least one scramble signal; and a band pass filter connecting the output of said filter to a phase-locking loop in said processing means.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers; filter means for filtering out said at least one scramble signal from said television receiver circuits;
phase-locking means for phase locking the at least one said scramble signal relative to said video carrier signal;
said phase locking means comprising:
mixer means for mixing said at least one scramble signal with a signal equal to the difference between said video carrier signal and said at least one scramble signal; and a band pass filter connecting the output of said filter to a phase-locking loop in said processing means.
7. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits; and pre-emphasis amplifying means for amplifying the video carrier in a narrow band about the frequency of the at least one scramble signal.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits; and pre-emphasis amplifying means for amplifying the video carrier in a narrow band about the frequency of the at least one scramble signal.
8. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
said filter means comprising:
a sharply tuned notch filter having a narrow band width approximately symmetrical about the frequency of the at least one scrambling signal.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
said filter means comprising:
a sharply tuned notch filter having a narrow band width approximately symmetrical about the frequency of the at least one scrambling signal.
9. The television security system according to claim 8 wherein said notch filter has an attenuation of at least minus 45db.
10. The television security system according to claim 7 including a pre-emphasis amplifier for amplifying a video carrier in a narrow band width about the frequency of the at least one scrambling signal.
11. The television security system according to claim 10 wherein the band width of the notch filter and the pre-emphasis amplifier are approximately equal so that they counter-balance each other to minimize degradation of video information.
12. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers.
13. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television recievers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
wherein the amplitude of said at least one scramble signal is at a 0 db level relative to the video carrier of said television signal.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television recievers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
wherein the amplitude of said at least one scramble signal is at a 0 db level relative to the video carrier of said television signal.
14. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television recievers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said step of generating the scramble signal comprising:
generating at least one scramble signal at a frequency approximately midway between the frequencies of said video carrier and audio carrier.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television recievers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said step of generating the scramble signal comprising:
generating at least one scramble signal at a frequency approximately midway between the frequencies of said video carrier and audio carrier.
15. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers; and modulating said at least one scrambled signal at 15 Hz and 1 KHz.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers; and modulating said at least one scrambled signal at 15 Hz and 1 KHz.
16. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said filtering step comprising:
filtering a narrow band of said video carrier at approximately--45db.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said filtering step comprising:
filtering a narrow band of said video carrier at approximately--45db.
17. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers; and pre-emphasizing a narrow band of the video carrier at the frequency of the scramble signal;
said filtering step comprising:
filtering a narrow band of said video carrier at approximately--45db;
whereby said filtering and pre-emphasis counterbalance each other to minimize degradation of the video information.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers; and pre-emphasizing a narrow band of the video carrier at the frequency of the scramble signal;
said filtering step comprising:
filtering a narrow band of said video carrier at approximately--45db;
whereby said filtering and pre-emphasis counterbalance each other to minimize degradation of the video information.
18. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers; and phase-locking the at least one scramble signal to the video carrier.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers; and phase-locking the at least one scramble signal to the video carrier.
19. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
phase-locking the at least one scramble signal to the video carrier;
wherein said phase-locking step comprises mixing the at least one scramble signal with a signal having a frequency equal to the difference between the scrambled signal and the video carrier;
filtering the signal recieved after mixing;
connecting the output of said filter to a phase-locked loop in the processor.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
phase-locking the at least one scramble signal to the video carrier;
wherein said phase-locking step comprises mixing the at least one scramble signal with a signal having a frequency equal to the difference between the scrambled signal and the video carrier;
filtering the signal recieved after mixing;
connecting the output of said filter to a phase-locked loop in the processor.
20. The method according to claim 19 wherein said phase-locking step includes:
phase-locking the scrambled signal at a frequency approximately midway between the video carrier and the audio carrier.
phase-locking the scrambled signal at a frequency approximately midway between the video carrier and the audio carrier.
21. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency;
wherein the frequency of the at least one scramble signal is approximately 2.25 MHz above the video carrier frequency.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency;
wherein the frequency of the at least one scramble signal is approximately 2.25 MHz above the video carrier frequency.
22. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency;
wherein the frequency of the at least one scramble signal is selected to be close to a multiple of the horizontal sweep frequency than the vertical frequency.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency;
wherein the frequency of the at least one scramble signal is selected to be close to a multiple of the horizontal sweep frequency than the vertical frequency.
23. A television security system comprising:
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency;
wherein the frequency of the scramble signal is 2.257 MHz, selected to be closer to a multiple of the horizontal sweep frequency that the vertical frequency.
processing means for processing a television signal having a video carrier and audio carrier;
scramble signal generating means for injecting at least one scrambling signal having a frequency between the video and audio carriers of said television signal such that said television signal is scrambled thereby, said at least one scrambling signal having a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video carrier and the audio carrier;
transmitting means for transmitting said scrambled television signal to television receivers;
filter means for filtering out said at least one scramble signal from said television receiver circuits;
wherein said scramble signal generator means includes oscillator means for producing at least one scramble signal at a frequency approximately midway between the video carrier signal frequency and the audio carrier signal frequency;
wherein the frequency of the scramble signal is 2.257 MHz, selected to be closer to a multiple of the horizontal sweep frequency that the vertical frequency.
24. A method of securing a television channel transmission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said step of generating the scramble signal comprising:
generating at least one scramble signal at a frequency approximately midway between the frequencies of said video carrier and audio carrier, and generating the at least one scramble signal at a frequency of approximately 2.25 MHz above the video carrier frequency.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one-fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said step of generating the scramble signal comprising:
generating at least one scramble signal at a frequency approximately midway between the frequencies of said video carrier and audio carrier, and generating the at least one scramble signal at a frequency of approximately 2.25 MHz above the video carrier frequency.
25. A method of securing a television channel trans-mission comprising:
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said step of generating the scramble signal comprising:
generating at least one scramble signal at a frequency approximately midway between the frequencies of said video carrier and audio carrier, and generating the at least one scramble signal closer to a multiple of the horizontal sweep frequency than the vertical frequency.
processing a television signal having a video carrier and an audio carrier;
generating at least one scramble signal at a frequency substantially in the range of one fourth to three-fourths of the frequency interval between the video and audio carriers of the television signal;
combining said television signal with said at least one scramble signal at the output of said processor such that the television signal is scrambled thereby;
transmitting said scrambled television signal to a plurality of television receivers;
filtering out said scramble signal from said scrambled television signal at the input to the television receivers;
said step of generating the scramble signal comprising:
generating at least one scramble signal at a frequency approximately midway between the frequencies of said video carrier and audio carrier, and generating the at least one scramble signal closer to a multiple of the horizontal sweep frequency than the vertical frequency.
26. The method according to claim 25 including:
generating the at least one scramble signal at a frequency of 2.257 MHz above the video carrier frequency.
generating the at least one scramble signal at a frequency of 2.257 MHz above the video carrier frequency.
27. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby; and transmitting means for transmitting said scrambled televison signal for television reception.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby; and transmitting means for transmitting said scrambled televison signal for television reception.
28. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, having a frequency substantially midway between the video carrier signal frequency and the audio carrier signal frequency, such that said television signal is scrambled thereby, and transmitting means for transmitting said scrambled television signal for television reception.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, having a frequency substantially midway between the video carrier signal frequency and the audio carrier signal frequency, such that said television signal is scrambled thereby, and transmitting means for transmitting said scrambled television signal for television reception.
29. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and modulating means for modulating said at least one scramble signal at 15 Hz and 1 KHz.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and modulating means for modulating said at least one scramble signal at 15 Hz and 1 KHz.
30. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby; and transmitting means for transmitting said scrambled television signal for television reception;
wherein the amplitude of said at least one scramble signal is at 0 db relative to the video carrier of said television signal.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby; and transmitting means for transmitting said scrambled television signal for television reception;
wherein the amplitude of said at least one scramble signal is at 0 db relative to the video carrier of said television signal.
31. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and phase-locking means for phase locking the at least one scramble signal relative to said video carrier signal.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and phase-locking means for phase locking the at least one scramble signal relative to said video carrier signal.
32. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and phase-locking means for phase locking the at least one scramble signal relative to said video carrier signal;
said phase-locking means comprising:
mixer means for mixing said at least one scramble signal with a signal equal to the difference between said video carrier signal and said at least one scramble signal; and a band pass filter connecting the output of said filter to phase-locked loop in said generating means.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and phase-locking means for phase locking the at least one scramble signal relative to said video carrier signal;
said phase-locking means comprising:
mixer means for mixing said at least one scramble signal with a signal equal to the difference between said video carrier signal and said at least one scramble signal; and a band pass filter connecting the output of said filter to phase-locked loop in said generating means.
33. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and pre-emphasis amplifying means for amplifying the video carrier in a narrow band about the frequency of the at least one scramble signal.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and pre-emphasis amplifying means for amplifying the video carrier in a narrow band about the frequency of the at least one scramble signal.
34. The invention as set forth in claim 33 including a pre-emphasis amplifier for amplifying a video carrier in a narrow band width about the frequency of the at least one scrambling signal.
35. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and eliminating means for eliminating said at least one scramble signal from said television signal before reception by television receiver circuits.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception; and eliminating means for eliminating said at least one scramble signal from said television signal before reception by television receiver circuits.
36. A television security system comprising:
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception;
eliminating means for eliminating said at least one scramble signal from said television signal before reception by television receiver circuits;
said eliminating means comprising a sharply tuned notch filter having a band width about the frequency of said at least one scrambling signal.
means for generating a television signal having a video carrier and an audio carrier;
scramble signal generating means for injecting at least one scramble signal between the video and audio carriers of said television signal, said at least one scramble signal having a frequency substantially between the limits of one-fourth and three-fourths of the frequency interval between said video carrier and said audio carrier, such that said television signal is scrambled thereby;
transmitting means for transmitting said scrambled television signal for television reception;
eliminating means for eliminating said at least one scramble signal from said television signal before reception by television receiver circuits;
said eliminating means comprising a sharply tuned notch filter having a band width about the frequency of said at least one scrambling signal.
37. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby.
38. The method as set forth in claim 37 wherein the step of generating the at least one scramble signal comprises:
generating the at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier.
generating the at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier.
39. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially midway between the frequency of the video carrier and the frequency of the audio carrier;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially midway between the frequency of the video carrier and the frequency of the audio carrier;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby.
40. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the adio carrier are scrambled thereby; and modulating said scramble signal at substantially 15 Hz and 1 KHz.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the adio carrier are scrambled thereby; and modulating said scramble signal at substantially 15 Hz and 1 KHz.
41. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby; and filtering out said scramble signal.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby; and filtering out said scramble signal.
42. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby;
filtering out said scramble signal;
said filtering step comprising filtering a narrow band of said video carrier at approximately--45db.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby;
filtering out said scramble signal;
said filtering step comprising filtering a narrow band of said video carrier at approximately--45db.
43. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby; and pre-emphasizing a narrow band of the video carrier at substantially the frequency of the scramble signal to minimize degradation of video information.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby; and pre-emphasizing a narrow band of the video carrier at substantially the frequency of the scramble signal to minimize degradation of video information.
44. A method of securing television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby; and phase locking the scramble signal to the video carrier.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby; and phase locking the scramble signal to the video carrier.
45. A method of securing a television transmission comprising:
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby;
phase locking the scramble signal to the video carrier;
said phase locking step comprising mixing the scramble signal with a signal having a frequency substantially equal to the difference between the scramble signal and the video carrier, filtering the signal received after mixing, the directing the filtered signal to a phase-locked loop in the processor.
generating a television signal having a video carrier and an audio carrier;
generating at least one scramble signal having a frequency substantially within the range of one-fourth and three-fourths of the frequency interval between the video carrier and the audio carrier of the television signal;
combining said television signal with said at least one scramble signal such that the video carrier and the audio carrier are scrambled thereby;
phase locking the scramble signal to the video carrier;
said phase locking step comprising mixing the scramble signal with a signal having a frequency substantially equal to the difference between the scramble signal and the video carrier, filtering the signal received after mixing, the directing the filtered signal to a phase-locked loop in the processor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/697,507 US4074311A (en) | 1976-06-18 | 1976-06-18 | Television security system |
| US697,507 | 1976-06-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1123950A true CA1123950A (en) | 1982-05-18 |
Family
ID=24801392
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,865A Expired CA1123950A (en) | 1976-06-18 | 1977-06-17 | Television security system |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4074311A (en) |
| CA (1) | CA1123950A (en) |
Families Citing this family (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4099203A (en) * | 1977-01-05 | 1978-07-04 | Joseph Garodnick | Television signal scrambling with introduction of replacement program signals |
| US4148064A (en) * | 1978-01-09 | 1979-04-03 | Gte Sylvania Incorporated | Jamming circuit for television signals |
| US4222067A (en) * | 1978-06-23 | 1980-09-09 | Stern Joseph L | Tamper-resistant television signal scrambling |
| DE3485639D1 (en) | 1983-10-31 | 1992-05-14 | Rf Monolithics | METHOD AND APPARATUS FOR TELEVISION VENTILATION AND UNEVOLVING. |
| US4638357A (en) * | 1984-01-20 | 1987-01-20 | Home Box Office, Inc. | Audio scrambler |
| US4682359A (en) * | 1984-10-15 | 1987-07-21 | Blonder-Tongue Laboratories, Inc. | Television picture and sound scrambler and method |
| US4825468A (en) * | 1986-10-24 | 1989-04-25 | Broadband Engineering, Inc. | Video noise jammer |
| US5068893A (en) * | 1986-11-04 | 1991-11-26 | Scientific Atlanta, Inc. | Television signal processing network for subscription television jamming signals |
| US4748667A (en) * | 1986-11-04 | 1988-05-31 | Scientific Atlanta | Jamming signal scrambling and descrambling systems for CATV |
| US4825467A (en) * | 1986-11-25 | 1989-04-25 | International Telesystems, Inc. | Restricted access television transmission system |
| US4802213A (en) * | 1987-02-26 | 1989-01-31 | Zenith Electronics Corporation | Sound masking in phase reversal TV scrambling system |
| JPS63292790A (en) * | 1987-05-23 | 1988-11-30 | Sony Corp | Dispersal signal removing circuit |
| US4841569A (en) * | 1987-12-30 | 1989-06-20 | General Instrument Corporation | Secure video distribution system |
| US5014309A (en) * | 1988-03-10 | 1991-05-07 | Scientific-Atlanta, Inc. | Off-premises cable television channel interdiction method and apparatus |
| US5303295A (en) * | 1988-03-10 | 1994-04-12 | Scientific-Atlanta, Inc. | Enhanced versatility of a program control by a combination of technologies |
| US5287539A (en) * | 1988-03-10 | 1994-02-15 | Scientific-Atlanta, Inc. | Interdiction program denial system for jamming audio and video signals |
| US5040211A (en) * | 1988-10-13 | 1991-08-13 | Massachusetts Institute Of Technology | Reliable television transmission through analog channels |
| US4951313A (en) * | 1989-12-07 | 1990-08-21 | Synchronous Communications, Inc. | Scrambled frequency modulated video signal transmission system |
| US5022078A (en) * | 1990-03-08 | 1991-06-04 | Andrew F. Tresness | Television signal enhancement and scrambling system |
| US5185793A (en) * | 1991-03-15 | 1993-02-09 | Eagle Comtronics, Inc. | Method and apparatus for securing television signals using sideband interdiction |
| US5278525A (en) * | 1992-06-11 | 1994-01-11 | John Mezzalingua Assoc. Inc. | Electrical filter with multiple filter sections |
| US5726606A (en) * | 1996-07-17 | 1998-03-10 | Eagle Comtronics, Inc. | Pre-emphasis network with variable time delay |
| US6081599A (en) * | 1997-12-01 | 2000-06-27 | Tresness Irrevocable Patent Trust | Saw television scrambling system |
| CN100452075C (en) * | 2006-01-27 | 2009-01-14 | 北京飞天诚信科技有限公司 | Security control methods for date transmission process of software protection device and device thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2905747A (en) * | 1953-09-22 | 1959-09-22 | Rca Corp | Secrecy systems |
| US3202758A (en) * | 1961-11-09 | 1965-08-24 | Paramount Pictures Corp | Subscription-television programscrambling system |
| GB1041405A (en) * | 1963-04-16 | 1966-09-07 | R & R Res Ltd | Improvements in or relating to television systems |
| US3760097A (en) * | 1972-06-26 | 1973-09-18 | Hughes Aircraft Co | Adjacent catv channel jamming |
| US3896262A (en) * | 1974-03-21 | 1975-07-22 | Hughes Aircraft Co | Subscription television jamming system |
-
1976
- 1976-06-18 US US05/697,507 patent/US4074311A/en not_active Expired - Lifetime
-
1977
- 1977-06-17 CA CA280,865A patent/CA1123950A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4074311A (en) | 1978-02-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19990518 |