KR100231088B1 - Interdiction device and method with variable retention time - Google Patents

Abstract

The cable television interdiction device 130 according to the present invention includes a microprocessor operation and control means 300 for operating and controlling one or more frequency sensitive voltage controlled oscillators 341-344, which are controlled by the voltage controlled oscillator 341. -344 selectively jams only unlicensed premium programming data sent from the headend 100 to a particular subscriber. In addition, the interdiction method according to the present invention provides a voltage control word for operating the oscillators 341-344 and an addressable transmitted and stored premium programming permission data to match the selective jamming factor of the headend for the particular channel to be jammed. Generating and storing.

Description

[Name of invention]

Interdiction device and method with variable retention time

Detailed description of the invention

[Related Applications]

This application is part of US Patent Application No. 166,302, filed March 10, 1988. See also "Picture Carrier Control Circuit for Cable Television Interdiction or Jamming Apparatus," "Optimum Amplitude And Frequency." Mooring, filed December 6, 1989, entitled "CATV Reverse Path Manifold System" and "CATV Subscriber Disconnect Switch" of Jamming Carrier In Interdiction program Denial System See co-owned applications in progress.

[Background of invention]

[Technical Field]

TECHNICAL FIELD The present invention relates to a cable television system, and more particularly to remotely controlled and authorized interdiction or jamming signals to prevent the reception of unauthorized ("unauthorized") television channels. A method and apparatus for providing the same.

Background Technology

The headend of a cable television system is generally provided with a scrambler for encoding a premium television channel. Scrambling prohibits reception by an unlicensed converter / decoder at the connected premises. Data representing a channel or tier of programming is addressably transmitted to a particular converter / decoder and stored in a licensed memory. When data is transmitted in an addressing manner, the sequentially transmitted programs are allowed, so that the decoder section of the converter / decoder will be selectively enabled to decode the scrambled premium channel or program.

Several types of scrambling techniques have been used in recent years. Each manufacturer has its own way of operating that is incompatible with the other. Nevertheless, today's most popular scrambling system is based on sync suppression, which moves the sync information to the level occupied by the picture information (equivalent to 40 IRE units at the end of sync). It is common to move to the image level) so that the synchronization information is hidden from the synchronization separator of the television receiver. Some systems modulate the image carrier with a phase adjusted sinusoid to suppress the horizontal blanking period. Most systems today switch to the suppressed level at the beginning of the blanking period and end the switching at the end of the period, suppressing most, if not all, of the vertical blanking period. Other systems dynamically invert the image either line-by-line or field-by-field. This should be done carefully to avoid artifacts caused by inversion and reversal at different levels and the differential gain and phase of the system. Synchronization is restored by providing a synchronous amplitude modulation pulse on the voice carrier or by phase modulation on a digital information or image carrier located in a vertical period.

Providing one scrambler per premium channel at the headend and a descrambler at each converter / decoder at the premises of a television receiver is particularly expensive. In addition, providing a converter / decoder to the premises has been of great interest to service intruders who have been looking for ways to receive premium channels. As a result, cable television equipment manufacturers have created complex service licensing protocols, including, for example, multiple layers of encryption by means of in-band and out-of-band data transmissions, in order to fight these intruders. The price of the converter / decoder has risen further.

In addition, all scramble systems will leave stepped artifacts on the front and rear porches in the horizontal blanking period. Under normal circumstances this is not a problem, but if the television receiver does not have a suitable overscan, staircase artifacts may appear as lightbars on one or both sides of the image. And if the television receiver uses back capture sampling for automatic gain control and / or black level recovery and the sampling period is extended to the time of the descrambling step, poor black levels appear on the television and flicker occurs in the image. May appear. In systems where pulse trains are applied to voice carriers, buzz carried by harmonics of 59.94 Hz signals may appear in some television receivers.

As a result, the cable TV industry has sought new technologies, and early development technologies, such as the use of negative and positive traps, and more recent technologies such as interdiction. It appeared.

Bootlab technology has been recognized by many manufacturers as an excellent alternative to the method of synchronous suppression scrambling. Bootlab's default narrowband rejection filter. Boottraps and fixed traps are located at the relay site of the subscriber's residence and attenuate important portions of the premium television channel that prevent the channel from being used by the subscriber.

In a typical embodiment, the boot wrap is made using L-C filter technology. The result is a notch with finite goodness Q and finite shape factor. In the case of a single channel bootstrap, the center of the notch is typically located at the image carrier frequency of the channel to be removed. Also known as static bootstrap, the technique requires at least 60 dB of image carrier attenuation.

The boot wrap method has several advantages that attract attention for cable TV applications. One major advantage is the ability to deliver broadband cable television spectrum to the subscriber's converter / decoder. Conventional synchronous suppression systems employ a descrambling set-top converter / decoder that carries narrowband signals according to their inherent characteristics. Bootwrap can be mounted outdoors (usually a tap) of a subscriber, thereby minimizing exposure to installing hardware inside the subscriber's residence. Finally, some cable TV operators recognize the boot wrap method as a more secure subscriber control means than the sync suppression method, as image reconstruction is considered to be substantially more difficult.

However, the boot wrap method requires hardware that has no benefit for the cable television system. Moreover, Bootlap has some serious practical limitations. L-C band rejection filters have Q and form factor limitations. The goodness Q of the L-C filter is usually limited to 30 or less. This means that for a boot wrap located on channel 8 (picture carrier at 181.25 MHz), the 3 dB bandwidth of the boot wrap will typically be 6 MHz (or the bandwidth of the reference band television channel). This trap will result in significant degradation of the lower adjacent channel. The television receiver tuned to the lower adjacent channel will then contend with an additional 6 dB reduced voice carrier rather than competing with a 15 dB image-to-audio ratio. Frequency stability as a function of time and temperature is also an important concern. Many cable television system operators often organize regular boot wrap change programs based on the assumption that frequency drift after a given time and temperature cycle renders the boot wrap useless.

Cascadability is also an important concern. Finite retrurn loss and non-zero insertion loss limit the number of single channel bootstraps that can be cascaded. As the number of services that need to be secured increases, bootlap decreases inversely. Moreover, changes in the channel lineup in this way require significant investment of hardware and labor.

Recently, a new type of bootstrap has been introduced. Dynamic bootstrap is a notch filter designed to be modulated with respect to frequency. The notch is centered around the image carrier but with some deviation in the lateral direction. Television channels can be disabled if unwanted amplitude and phase modulation is introduced on the image carrier. This technique requires significantly less notch depth (typically 40 dB) compared to static bootstrap. In addition, by introducing frequency modulation arbitrarily, the need for frequency stability can be reduced.

However, dynamic boot wrap has some drawbacks. A power source is needed to perform frequency modulation. More important is parasitic modulation created on adjacent television channels by this dynamic boot wrap technique.

The static trap method also uses a narrowband rejection notch filter. However, unlike the bootstrap method used to attenuate or trap premium channel transmissions, notch filters are used to recover premium television channels. In this way, the cable television headend generates interference signals on premium television channels. The interfering signal is then removed by the notch filter in the subscriber premises. This notch filter is ideal for removing only interfering signals without removing a significant amount of television information.

Jeong trap technology seems to have some disadvantages for cable television system operators. It is considered advantageous to have interference present in the secure channel at the cable television relay station (unlike the boot wrap method where the channel to be secured is 'clear' at the relay station). Economically, it is very attractive that subscribers only need subscriber hardware where they want to receive security services. Thus, some capital investments are associated with revenue generation.

A typical embodiment of the forward trap method uses an L-C notch filter to remove the interfering signal. This L-C notch filter is subject to the same limitations as in the case of the L-C bootstrap described above. As a result, the L-C forward trap is limited to the lower end of the cable television spectrum. Goodness Q and shaping factor also limit the number of places for interfering signals in a television channel.

In a typical embodiment of the forward trap system, the location for the interfering signal is the middle part of the image carrier and the voice carrier. The energy density (ie information density) in this region of the spectrum is relatively low. One reason for this choice is that jamming is done unless the television, which improves the goodness of the recovered television signal by minimizing the television information removed with the interference signal by the notch filter, does not perform particularly bad removal above 2.25 MHz of the picture carrier. It will be common for the carrier to exhibit minimal effect on television images of adjacent channels. This jammer adds another carrier which the tuner must contend with and which may cause some degradation in the event of a marginal overload.

Notwithstanding this case, the limitations of goodness Q and shaping factor of a conventional L-C fixed trap eliminate a significant amount of useful television information. As a result, remarkable softening of television images occurs with attenuation of high frequency information. Predistortion at the headend can improve this performance but cannot correct it completely. The place for such interfering signals also facilitates the work of video intruders. This intruder can easily tolerate the degraded signal and is therefore readily available (e.g., using the classic twin lead quarter wavestub with aluminum thin film sliders for precise tuning). It is possible to recover possible images, and the forward trap method has a higher cost per premium channel than the boot trap method.

A relatively recent technique for premium channel control is an interdiction system named because of the introduction of interference signals at subscriber locations. Most embodiments of this system consist of a pole-mounted enclosure designed to perform for four or more subscribers. This enclosure includes at least one microprocessor controlled oscillator and switch control electronics to maintain several television channels. Control is achieved by injecting an interference or jamming signal from this pole mounted enclosure into the unlicensed channel.

For efficiency purposes, techniques are known for using one oscillator to jam a premium television signal. This technology not only reduces the amount of hardware required but also maximizes system flexibility. The output jamming signal frequency of the oscillator is sequentially shifted to each channel. As a result, the oscillator is frequency sensitive and jumps one jamming premium channel frequency to the next.

One example of such a system is known by US Pat. No. 4,450,481, in which a single frequency sensitive oscillator provides a hopping gain control jamming signal output to four high frequency electronic switches. Each switch is associated with one subscriber zone. Depending on whether the subscriber is authorized to receive premium programs transmitted under microprocessor control, the microprocessor selectively gates through the switch a path that delivers a wideband television signal to each subscriber that has arrived at the output of the jamming signal of a single oscillator. . As a result, upon tuning of the program channel, an unlicensed subscriber will receive a premium channel with overlapping jamming signals at approximately the same frequency.

The known system indicates that 16 channels can be jammed by a single voltage controlled frequency sensitive oscillator. For one premium channel this translates into a situation where the jamming signal can only appear during a jamming period of 1/16 or about 6% of the time. The absorbing ratio also appears as 100 bursts per second or 100 Hz hopping ratio of the jamming signal at a particular frequency. As a result, the validity of the jamming signal can be a problem.

Cable television channels and premium services can range from a wide range of frequencies, such as 100 to 350 MHz. In this known embodiment, the single oscillator provided should be frequency sensitive over a wide range. In addition, the jamming signal output of a single oscillator must be within the range of 100-500 KHz or above the video carrier frequency. As a result, a synthesizer with an internal reference is provided to accurately maintain the oscillator's jamming signal output up to the allowable 100-500 KHz band above and below the video carrier.

Jamming signals occur at relatively high power and exhibit gains that are controlled to exceed the amplitude of the video carrier by 5-20 dB. Such interdiction systems have significant improvements since the output power is higher compared to premium channel video carriers and it is difficult to accurately jam the premium channel frequency. Since the oscillator has frequency hopping, its spectrum may be scattered around the picture carrier, resulting in slightly different situations as long as the adjacent channel rejection characteristics of the television are required.

First, it is important to control the jamming frequency so that interference is as close as possible to the image carrier. Second, it is also important to limit the peak amplitude of the interfering signal so that it does not exceed the video peak envelope power significantly in order to avoid artifacts in adjacent channels. However, in known systems, adjacent channel artifacts occur because the jamming signal is intentionally located below the video carrier and eventually approximates to the adjacent channel. In addition, the frequency hopping speed is limited in the known embodiment because the conventional frequency control technique is applied during the hopping process.

Known interdiction systems have proven to be prone to adjacent channel artifacts from the aforementioned amplitudes and frequency and frequency selections that may be complaining to subscribers. Moreover, the main perception of depth jamming an unlicensed premium channel is relatively unsatisfactory because it is limited to a maximum 6% jamming interval when 16 premium channels are jammed with a single oscillator and relatively low frequency hopping rate.

[Overview of invention]

Many of the above-mentioned conventional problems and their related problems are solved by the principles of the present invention, and the television channel interaction method and apparatus can remotely control the jamming depth and frequency with reduced power. After considerable investigation and experimentation of the known techniques, the optimal position of the jamming signal is approximately in the range extending from the video carrier to the upper 250 KHz of the video carrier and much lower jamming signal position than the video carrier generates artifacts in the next lower adjacent channel. do. This position is between the video carrier and the audio carrier for the same premium channel. In addition, the jamming carrier is a digital stepwise selectable frequency within the upper 250 KHz range of the video carrier from the head end can be accurately set to a frequency resolution of 50 KHz. The 10-bit voltage control word is applied to the voltage controlled oscillator by a digital / analog converter to control the frequency of the jamming signal within the frequency range or to provide a jamming signal outside the range, for example, when the audio carrier is intentionally jammed. do. Furthermore, in order to ensure the frequency accuracy of the jamming signal and to limit the jamming signal frequency harmonic interference, a plurality of oscillators are provided, each operating in a particular narrow band of the cable television spectrum. The sum of all such narrowbands is equal to the entire spectrum where jamming is desired, indicating whether the cable television spectrum to be jammed can be discontinuous or what overlap of bands is required. In particular, four separate oscillators are provided whose outputs are individually filtered to eliminate the appearance of harmonics in the jamming signal output that can interfere with the reception of television signals on other higher channels in the spectrum. Each oscillator is intentionally limited to jamming up to four channels in its band and generates approximately one coefficient for four improvements in the jamming interval compared to the prior art. Each of the plurality of oscillators is also provided per subscriber base or per premises base.

According to the principles of the present invention the jamming signal power is limited in the range of -3.5 dB to +6.5 dB and normally has +2 dB relative to the video carrier power level. Thus, there is less opportunity for adjacent channel interference than in conventional systems.

The jamming depth, ie the main perception of a person watching a scrambled television channel on a number of different television receivers, is improved by improving the frequency hopping speed to approximately 4 KHz, increasing the coefficient at the speed of the known system and the amplitude and frequency of the jamming signal. All other parameters, such as, become the same. As described herein, embodiments of the present invention can achieve frequency hopping rates of this magnitude because they are not limited by conventional frequency synchronization techniques.

The microprocessor of the device also controls the power supply to the multiple oscillators. If a subscriber is authorized to receive all premium channels in the band defined by a given oscillator, the oscillator may degrade power during that period. The remaining jamming signal output power is also intentionally passed through the open switch during power up conditions, as is the case with conventional interdiction systems.

The common circuit is shared by up to four subscribers, for example, and is provided in the form of pole mounting, wire mounting or foundation mounting. The common circuit includes an automatic gain control circuit for adjusting the level of the video carrier. The common circuit also includes a data receiver, a data decoder and a microprocessor that are individually addressed. The common circuitry individually decrypts each addressed command or data sent from the headend at the service subscriber module. The microprocessor of the common circuit communicates any decrypted data relating to the particular subscriber used in the subscriber module with the microprocessor of the coercion module. The decrypted data represents, for example, individually addressed channel or program permission data or globally transmitted channel frequencies and jamming depth data received from the headend for storage in microprocessor memory. During normal operation mode, the subscriber module's microprocessor operates each required oscillator to drive frequency data towards all required oscillators to jam any or all unlicensed channels with the jam coefficient selected for each particular premium channel. send. In particular, 64 memory location memories can be reserved to store 10-bit voltage control words. The algorithm of the subscriber module microprocessor loads the voltage control word memory depending on the service level selected by the subscriber. In the extreme case that a particular subscriber is authorized to receive all premium channels, only one of the three oscillators can be operated and the other oscillator can jam one unlicensed channel continuously, resulting in a 100% jamming interval.

If a particular subscriber at a given time point is reserved such that none of the 16 channels are provided, all four oscillators are triggered in succession and 64 voltage control words are provided in pseudo random order towards the four oscillators. Authorization of such pseudo-random order can prevent infringement.

The jam coefficient defined here is a selectable parameter and is transmitted globally by the headend to equal the relative degree of jamming to be applied to other premium channels. For example, it is appropriate to jam a highly limited programming with a high jam coefficient. According to the present invention, a total of 16 voltage control words may be allocated to one premium channel. Eventually, it is similar to the jamming time slot interval that can be allocated by the headend to improve the 16 control word jamming depths. For example, if three premium programs are provided by the headend for a channel in an oscillator's assigned band at a particular time point, the 16 time slots or the corresponding jam coefficients would overlap 5% for the last jamming channel. Are assigned to 8, 4, 4 (16 total) to run at least 20% jamming intervals. As already explained, if a subscriber reserves all three of these channels, the microprocessor algorithm either de-energizes the oscillator as a whole or increases the jamming interval relative to the extent of the reserved premium service and the assigned jamming coefficient.

According to the novel feature of the present invention, the time at which a particular channel is jammed can be changed (to increase the jam coefficient) so that an operator jams much richer any channel requiring more security. Moreover, the dead time can be changed randomly and more than one time slot can be assigned to a particular channel per cycle. In addition, a plurality of consecutive time slots may be allocated to a specific channel.

Periodically and upon powering up, the apparatus of the present invention enters the mode of adjustment operation, eg every 30 minutes. Premium channel frequency data is transmitted globally from its front end for storage in the memory of the microprocessor of the common circuit. The common circuit microprocessor then divides by the coefficient for the expected time between the programmable prescaler and the frequency coefficient of the subscriber module and sends the calculation to the microprocessor of each subscriber module.

A programmable prescaler or frequency separator is provided in the feedback path from the plurality of oscillators to the microprocessor of the subscriber module. Only one oscillator is powered during the adjustment mode. The transmitted and stored frequency data is translated into the voltage establishment word of the best estimate. As a result, only the jamming signal frequency of the power-up oscillator is fed back through the prescaler, which is separated into the high frequency output for computation by the microprocessor. The microprocessor calculates the coefficients according to the time interval between the prescaler's receive outputs. The count is then compared with the expected count and the voltage control word adjusted accordingly. After up to ten such calculations, starting with the most significant bit of the voltage control word, the particular control word is set correctly in the voltage control word memory. In order, all 16 control words or all 64 words of each oscillator are correctly set and only a few seconds are needed to carry out the overall procedure. As a result, if the subscriber tries to watch the unlicensed premium channel at the same time, no information is obtained during the coordination mode. Thus, with the provision of a plurality of narrowband oscillators, the coordination mode ensures control of the jamming signal frequency.

By means of the coordination mode of operation and structure of the present invention, the jamming carrier can be positioned substantially anywhere within the video carrier up to 250 KHz or, if necessary, to the jamming audio carrier. There is an opportunity for frequency shifting of a given jamming signal frequency during approximately 30 minute intervals with temperature changes. However, the frequency shift is desirable when there is concern of any infringement of detecting the jamming signal by the notch filter. As mentioned above, the jamming signal frequency can also be intentionally changed by changing the voltage control word jamming a given premium channel. They can also be applied in pseudo random order. Thus, in order to infringe, a plurality of notch filters must be operated sequentially, following the same pseudo random order and at the same frequency as indicated by the associated voltage control word, and for which the aforementioned natural frequency shift is expected to invade the premium television signal.

By using a coordinated mode of operation distinct from the normal mode of operation, the apparatus of the present invention can achieve much higher frequency hopping speed than conventional systems during normal mode of operation. The desired hopping speed of 3-4 KHz can be achieved since there is no need to apply conventional slow frequency synchronization techniques during normal operation mode.

The above and other advantages of the method and apparatus of the present invention for remotely and addressing control of interaction are described below with reference to the accompanying drawings.

[Brief Description of Drawings]

1 is an overall system block diagram illustrating the inherent compatibility of an interdiction device of the present invention with an existing cable terrellvision system having a premium channel scraper, an addressable data transmitter and a subscriber converter / decoder.

2 is a schematic circuit diagram of an addressable common control circuit for a plurality of subscriber modules according to the present invention having a wideband signal tap, a microprocessor, a data receiver and a decoder, and an automatic gain control circuit.

3 shows each of the four voltage controlled oscillators to ensure that 16 premium channels are jammed at a minimum of 20% jamming interval during normal operation mode and a feedback path through a programmable prescaler is provided to precisely set the jamming signal frequency during adjustment mode. A block diagram schematically depicting one subscriber module having a microprocessor for selectively activating and controlling the output frequency provided by.

4 is a frequency diagram for allocating a wideband cable television spectrum among four individual bands in each of four or more channels and a band having multiple channels where only four channels can be jammed at a 20% jamming interval.

5 is a detailed block diagram schematically illustrating one embodiment of a feedback loop structure for implementing the adjustment mode of operation of the present invention.

FIG. 6 is a block diagram illustrating a voltage controlled word memory in connection with sequentially providing a jamming frequency signal output of an oscillator during a normal operating mode.

FIG. 7 is a timing diagram of the embodiment shown in FIG. 3 in the normal operation mode, in which each interaction control signal is shown specifically. FIG.

8 illustrates several exemplary jamming patterns for jamming multiple channels with different dwell times.

[Preferred Embodiments of the Invention]

1 is an overall block diagram of a cable television system utilizing the principles of the present invention. Cable television system refers to an entire system for transmitting television signals to a remote location via a cable. For example, a cable television system may include a common antenna television distribution system (joint TV reception system), satellite signal reception system, broadcast television system, personal cable distribution network, industrial or educational, or other form of cable distribution network. Each remote area with a pressurizer is a particular subscriber who receives contracted television service. It may include areas with multiple subscribers, subscribers with multiple television receivers, or areas dedicated to dedicated cable distribution networks. A subscriber is used herein to refer to a dedicated subscriber or a general user of a cable television system. Head end 100 is defined herein as a slow point connected to a supply cable and distributes the necessary television channels to the subscriber area. For the main purpose, the Electronics Industry Association Standard Cable Television Frequency Allocation Table is used and cited herein. However, by describing the present invention as follows, a method for assigning other known standard or non-standard frequencies will be provided. In addition, non-standard composite television signals from the baseband National Television Subcommittee (NTSC) are used throughout the description. However, the spirit of the present invention applies equally to other standard or nonstandard baseband television signal formats.

Headend 100 includes a television program source 101. The television program source 101 may include an output of a satellite television receiver, a program generated in a television studio, program material received through a microwave or broadcast television line, an output of a cable television line, or any other television program source identical to the present invention. Will be. The program source material is supplied to the remote site via the supply cable 110, including teletext, videotex, audio program, utility data, or other form of communication device, without having to be limited to a conventional television.

Program material generated at program source 101 will premium or otherwise restrict or appropriately protect what is received at an unauthorized receiver region. Each channel and program to be protected to achieve this is typically scrambled by the scrambler 102 supplied to the headend 100. Premium channel or premium program is used herein to mean a channel or program that is to be protected from unauthorized recipients because the channel and program are in a premium or restricted state.

Typically, all premium programs transmitted in the cable television system are clearly transmitted, and an interdiction signal is supplied to the interdiction device 130 to jam the unauthorized program from being received.

Thus, during the transmission period in which the headend 100 clearly generates the premium program and the modified television program, the scrambler 102 will be provided so that the converter / decoder 150 is provided to the subscriber to restore the modified program transmission. In a specific embodiment, the converter / decoder 150 may be entirely replaced with the interdiction device of the present invention.

Headend 100 also typically includes an address data transmitter 103, which transmits global commands and data to all subscribers or directs communication for reception by a dedicated subscriber. This data communication is performed by a data carrier (actually 1082 MHz) divided in the cable television spectrum. In addition, the data will be transmitted on an unused empty channel of the television spectrum. Global instructions generally have the form of opcodes and data and addressing communications further have a unique address for a particular subscriber.

In another embodiment, this communication is actually in the form of an in-band frequency signal transmitted with the television channel superimposed on the audio carrier during the vertical injector of the video signal. This data communication complicates data reception in the interaction device according to the present invention and is appropriately eliminated. However, in-band frequency signals always require that any converter / decoder 150, known in the art, be operated.

As a result, the headend 100, the cable television supply cable 100, and the converter / decoder 150 and the television receiver 170 at a typical subscriber premises constitute a commonly known cable television system. The channel program or permit data is transmitted via cable 110 via an address data transmitter. In the cable area below the pole 120 or pedestal 140, the supply signal is supplied to the subscriber area via drop 115. Drop 115 is connected to a conventional converter / decoder 150 that provides various functions. In response to the addressed communication, the headend transmitter 103 writes the channel or program permission data to the permission memory when the address related to the addressed communication matches the unique address of the subscriber decoder 150. In practice, the subscriber address will consist of a number of bits significantly larger than the number of subscribers subscribed to the system and additional bits to ensure protection of the address. Premium channels and programs are stored in the allowable memory of converter / decoder 150. The television program changes from the converter portion of converter / decoder 150 to another unused channel, such as channels 3 or 4 of the television spectrum. The premium status is checked with reference to the data stored in the allowable memory. If the program is allowed, the decoder part of the converter / decoder is operated to protect the allowed and modified premium program.

The provided television receiver can be a conventional television receiver 170 or a cable television receiver 171. With the advent of the cable television receiver 171, the subscriber premises no longer need the converter portion of the same converter / decoder 150 that is embedded in the television receiver.

According to the cable television system provided with the interdiction device 130 of the present invention, the housing is mounted on the coupling cable 110 provided through the pole 120 or the pedestal 140. Inside the housing is a common control circuitry for tapping broadband television and data transmission spectra. Referring to the first pole 120 from the left side of FIG. 1, a device installed in a twisted pair provided with two drops 115 to be provided by the interaction device 130 is shown. Next to the common control circuit, four plug-in subscriber modules may be provided for one housing. In addition, additional services may be provided through other plug-in units in the housing, such as impulse viewing fees, subscriber polling including two-way communication, meter reading, energy management, or other services.

All equipment should preferably be removable from subscriber premises 182. However, in order to provide additional services, some equipment in the premises is necessary. For the purposes of this description, it is conceivable that premises 182 include at least one conventional television receiver 170 for a non-cable. As a result, the subscriber device must include a suitable converter for converting at least the received cable television channel into an empty channel, such as channel 3 or 4, which can be received by a conventional television receiver 170.

Power for the interaction device may be supplied from the headend 100 via a cable, through a subscriber drop 115, or a combination of the above means. Sooner or later, power can be supplied by means of recharging, such as solar cells, or by an internal source that can be exchanged, such as another external device or battery. As a result, the subscriber device 161 may be provided with a power source for the interaction device 130.

The interdiction device 130 may be protected by another device that is protected, such as in a locking device of a housing or apartment complex that cannot be tampered with. If the elements are located in an exposed location, the housing should be waterproof. In addition, the housing should be designed to prevent leakage of radio frequencies.

In the premises 183, it is assumed that the subscriber has a cable television receiver 171. Accordingly, the subscriber device 162 should completely remove or simply include the power supplied to the interdiction device 130.

Premise 184 represents the subscriber's zone provided by underground cable 110 via pedestal 140, which is a plurality of cable distribution amplifications. The premises are also typically provided with a track device and a drop 115. According to the present invention, the pedestal 140 may be configured off-premises according to the interdiction device 130. The subscriber device 162 is composed of a converter, an additional providing device, and a power supply, and is described according to the subscriber device 161, but the description of the subscriber device 162 is omitted.

The interaction device 130 may be designated as a single address by the headend 100 configured as the converter / decoder 150. Two bits of the plurality of bits of a single subscriber address are associated with a single plug-in slot as one of four subscriber modules. The common control circuit has a single address with residual address data that does not require data secure communication. Since the premium program is sent clear and no data communication is required with the subscriber premises, the subscriber address is not transmitted in secure form in accordance with the principles of the present invention. However, address security is desired if converter / decoder 150 or other single address mandatory device is provided in the premises.

The interaction device 130 is composed of a subscriber module having a common control circuit and four plug-ins. When the subscriber receives certain premium program or channel grant data, the data is stored in the interdiction device 130. The interaction device 130 further includes an automatic gain control circuit of the common control circuit. The channel interaction circuit jams each subscriber module an unlicensed program dropped to a particular subscriber via a particular drop 115. As a result, the interdiction device 130 is parallel and has addressable permission data transmission in the prior art. Premium channels do not require scramble. Moreover, the additional form of security provided is not necessary like channel encryption in in-band, other security measures, and channel changes. A service breacher may remove certain pseudo-random signals that are inserted at certain times located on a changing frequency, buy off-premises devices 130, or signal from shielded and mating cables 110 to secure from radio leakage frequencies. Will try to induce.

The common control circuit of the interaction device 130 is not shown in the second block diagram provided to the four subscriber modules according to the block diagram of FIG. According to FIG. 2, the supplier cable 110 enters the interdiction device 130 from the FEEDER IN and remains at the FEEDER OUT. The power PWR can be provided via the supplier cable with subscriber drop means by partial internal or external means.

The directional coupler 210 is connected to the broadband provision cable 110 in the form of a plug-in module tab. The wideband of the radio frequency signal is output to the high pass filter 220. The high pass filter 220 passes at least a frequency band consisting of the data carrier frequency or the bidirectionally used frequency and the cable television channel spectrum. According to FIG. 4, the cable television spectrum consists of a frequency from at least 120 MHz to 350 MHz.

The automatic gain control circuit includes a variable attenuator 230, an RF amplifier 233, a directional coupler 232, and an AGC control circuit 231. The automatic gain control circuit is roughly tuned to reduce the wideband RF signal power within a predetermined limit.

To receive data from address data transmitter 103 located at headend 100, data receiver 240 is coupled with directional coupler 232. The data receiver 240 transmits data on a carrier wave of 108.2 MHz and provides raw data to the data decoder 250. The data decoder 250 processes the data and individually transmits the data to the microprocessor 260 for interpretation according to an embedded algorithm. Microprocessor 260 is the most appropriately selected of the microprocessors provided for each subscriber module. Typical microprocessors use an 8-bit microprocessor with an internal 8 kilobyte, such as the Motorola 68HCO5C8.

The received data may be stored in the non-interruptible memory 270 by the microprocessor 260. Data is downloaded and stored for a long time when requested to the subscriber module via an external serial interface bus connecting to the microprocessor 260 having a separate microprocessor associated with the subscriber module in memory 270.

Thus, the microprocessor 260 interprets both global communications addressed to the common control circuit and communications addressed to a single subscriber module. When in use, microprocessor 260 ignores global or addressed communications to other interaction device 130 or converter inverter 150. An example of global communication for the interaction device 130 is premium channel frequency data and each premium program is provided through the headend 100. Examples of addressed communication include communication consisting of premium channel or program permission information or circuitry instructing common control circuitry to provide or cancel to a particular subscriber.

If bidirectional service over the supply cable is expected, the data imprinter, not shown, is provided in the common control circuit of FIG. 2 and has a separate telephone link from the subscriber zone to the headend. The serial external interface bus 290 enables bidirectional communication through the connection of the microprocessor 300 related to the subscriber module, and indicates the state of the microprocessor 260 being queried.

The radio frequency divider 280 supplies the wideband frequency signal to each subscriber module with at least the television serial spectrum cable of FIG.

If a reverse path is required by a particular additional service, it is required for a single synthesizer or plug-in special service module, not shown, to receive the communication signal from each of the four subscriber modules to divider 280 in the opposite way. Some data is sent back to the headend via a special service plug-in module associated with the additional special service.

3 shows an overall block diagram of a subscriber module according to the present invention. The microprocessor 300 is associated with a particular subscriber module and communicates with the microprocessor 260 of FIG. 2 via a serial peripheral interface bus. The microprocessor 300 is composed of an 8-bit microprocessor in which 2 kilobytes of microcode is embedded, and the microprocessor 300 reduces control response capability. As a result, the microprocessor 300 is configured to be similar to the Motorola 68CO5C3 microprocessor.

The inverted path is connected via a low pass filter 392 to a special service module of the common control circuit, as shown in FIG. 2, corresponding to the particular service module on the subscriber premises. The reverse path is connected to the subscriber through the terminal OS. Power is sent to the subscriber drop by the FIG. 3 module and recovered from the terminal OS.

From Figure 2 the broadband radio frequency television spectrum signal is provided to terminal IS. When the terminal IS is connected to the terminal OS with respect to the path, the service negative switch 389, the amplifier 387, the jamming signal multiplier 384, and the high pass filter are connected in turn. The denial of service switch 389 is controlled by the microprocessor 300. In the case of communications addressed from the headend 100, this indicates that the subscriber refuses to pay for the service. Services that negate switch 389 may be published. In addition, when the service is stopped, power may be cut off under the control of the microprocessor 387. In the case of having a plurality of television receivers having a normal number of subscribers or more, the amplifier 387 may be determined at a discrete gain level under microprocessor control.

The jamming signal is interdicted with the directional coupler under microprocessor control. Due to the directional characteristics of the amplifier 387, the jamming signal does not reach the second control or the common control circuit of the providing cable 110. The jamming signal is restrained at a level within the range of -2.5 dB to +6.5 dB or +2.5 dB, the video carrier low power level of the unlicensed premium channel frequency being jammed. Typically, video carrier jamming is suppressed in the extended frequency region up to +250 KHz, which is above the video carrier from the video carrier to the audio carrier of the jammed channel. Depending on the interaction device, the frequency can be selected by the headend 100 and, if desired, selected to jam the audio carrier at a frequency close to the carrier. In addition, the vibration level of the jamming signal may be changed through global data transmission, for example, when audio carrier jamming is required. This stop on all channels between the video and audio carriers minimizes adjacent channel artifacts.

The high pass filter 391 prevents any inverted path signal from reaching the combiner 385 and passes a wideband spectrum containing any jamming signal towards the terminal OS. For example, in this embodiment, the presence of an inverted path signal would result in a radio frequency signal below 100 MHz. The wideband television spectrum would fall in the 100-350 MHz range, consistent with FIG. However, the blocking of premium channel viewing may be allocated anywhere required within the jammed broadband or discontinuous cable TV spectrum. In conclusion, the filters 391 and 392 are designed according to this or similarly selected design criteria for blocking or passing the required wideband television or inverted path signals.

The microprocessor 300 controls one or more voltage controlled oscillators. According to a preferred embodiment four such oscillators 341-344 can be used, each of which oscillates the premium channel frequencies assigned to a continuous range of frequencies. However, the techniques of the present invention apply to many oscillators. Since premium programming can be transmitted anywhere in the cable TV spectrum, the sum of all these allocated portions makes up the entire television spectrum that is jammed. According to the present invention, the jammed television spectrum may comprise discrete portions or portions intentionally overlapping.

Referring briefly to FIG. 4, in one embodiment the spectral allocation for the four voltage controlled oscillators will be discussed in consideration of some principle. First, it is desirable to eliminate jamming signal harmonic interference for the assigned in-band grant channel. For example, 100 MHz, which is a harmonic of a relatively low frequency signal, can interfere with a channel by harmonics of this frequency in the upper portion of the cable TV spectrum. In other words, the allocated band is constrained so that the oscillator fits within one-third of an octave so that all frequency harmonics are blocked by filter 351, and all frequency harmonics are also associated with the filters 351, 352, 353, 354). Oscillator 341, denoted as OSC1, operates in a band between 126 and 158 MHz while the filter 351 blocks harmonics above the channels 15-20 in the middle band.

Cable headend service providers are likely to select premium channel assignments in the mid-band range across channels 15-22. Thus, the band of oscillator 342 may be selected to overlap the band allocated to oscillator 341.

To get a jamming interval of 20%, each oscillator can be limited to jamming only four premium channels. As described in connection with the fifth, sixth and seventh degrees, the jamming depth may be automatically increased for a particular subscriber depending on the subscriber's service level. In addition, by allocating overlapping bands between the first and second oscillators 341 and 342, all eight channels of the intermediate band leave the two high-band channels jammed by the oscillator 342. Can be jammed. Thus, according to FIG. 4, the oscillator OSC1 is assigned to the allocated six channel frequencies of the intermediate band while the oscillator OSC2 jams the redundant bands that make up the channels 19-20 of the middle band and the channels 7-10 of the high band. Can jam 4 of them. The range of jamming signal frequencies for oscillator OSC2 is chosen within the 150-194 MHz range, consistent with the elimination of desired harmonic interference.

According to this design principle, no redundant bands appear for oscillator OSC3 or oscillator OSC4. Nevertheless, the individual ranges of 198-254 MHz and 258-326 MHz of this oscillator eliminate any risk of harmonic interference. The low pass filters 353 and 354 block harmonic frequencies above the upper limit of these individual ranges. Oscillator OSC3 provides a jamming signal for jamming four premium channels of high band channels 11-13 and super bands selected from channels 23-29. The eight premium channels can be hindered by the reduced jamming factor for these ten channels. Oscillator OSC4 is provided for jamming to channel 41 from the super band channel 30 to the hyper band. Four of these twelve channels can be jammed at a 20% jamming interval. However, eight channels can be jammed by the reduced jamming element.

The microprocessor 300 is connected to the memory and buffer circuits that make up the RAMs 311 and 312 and the buffer 310 by the bus system. Microprocessor 300 operates at a clock frequency of 4 MHz provided to clock 336. Counter 335 is represented as a separate element. However, the counter 335 is provided to count the output frequency of the jamming oscillators 341-344 in essence while the adjustment mode is in operation and thus may constitute an element of the microprocessor 300.

The microprocessor 300 is connected to a D / A converter 320 which in turn converts the 10-bit voltage control word into an analog voltage output provided to the analog multiplexer 330. The analog voltage output of the analog multiplexer 330 is stored and maintained in the sample hold circuits 337-340 for use in the oscillators 341-344. Through a 2-bit parallel select bus, the analog voltage signal output is successively gated by analog multiplexer 330 which drives FREQ 1-4 towards oscillator 341-344. In accordance with the principles of the present invention, such signals may be provided in a pseudo-random sequence to prevent intrusion attempts to be described in connection with FIG.

The microprocessor 300 is connected to the individual oscillators 341-344 by individual oscillator power lines OPWR 1-4 to operate the oscillators. Each oscillator reduces energy consumption during normal operating mode if the subscriber is allowed to receive all channels in the allocated band at the appropriate point in time. In addition, during the calibration mode one oscillator may increase its energy consumption for adjustment while all other oscillators reduce their energy consumption.

The microprocessor 300 is further connected to four high frequency PIN diode switches 361-364. During normal operation, this switch is selectively opened for a short time interval of 16 microseconds when the associated oscillator is converted or jumped from one jamming signal frequency output to another jamming signal frequency output. Nevertheless, if four channels are jammed by a special oscillator with four jam coefficients, a 4,000 Hz frequency hopping rate can be easily obtained by this PIN diode switch.

Also, an associated low pass filter, provided to block all harmonic or jamming signal frequency outputs, is connected to each oscillator output. Such a low pass filter may be connected to the input or output of the switches 361-364 despite being connected in series between the associated oscillator and the high frequency switch shown in FIG.

All jamming signal outputs of the four oscillators are combined in signal combiner 365. The output coupled from the signal combiner 365 is coupled directly to the prescaler 375 and signal attenuator 380 programmable by the combiner 370.

Programmable prescaler 375 is only powered through read PREPWR when required during adjustment mode. According to the programmable splitting element, the splitting output frequency is provided to the microprocessor 300 for counting. When the energy consumption is reduced, no output signal is generated. During normal mode of operation, the combined jamming signal output of the attenuator 380 is coupled directly to the combiner 385 along with the incoming broadband television signal passed from the common control circuit of FIG. Since subscribers have to pay their bills, switch 389 and amplifier 387 are assumed to be powered. As a result of combining the jamming signal with the broadband spectrum (and therefore transmitted farther in the clear state), the subscriber will receive with a clear premium or limited programming that the subscriber is authorized to receive.

Turning now to FIG. 5 in more detail, a block diagram of one embodiment of a feedback loop useful for describing an adjustment mode of operation is shown. The adjustment mode occupying the second part ensures relatively stable frequency operation during normal operation mode. In addition, the adjustment mode eliminates the need for the application of slow conventional frequency locking techniques and a high operating frequency hopping speed of 4,000 Hz can be obtained during the normal operating mode. The embodiment represents the calibration of one particular oscillator OSC. The illustrated loop represents a specially applied integrated circuit ASIC connected to the subscriber module microprocessor 300. This circuit ASIC is clocked at twice the speed of the microprocessor and constitutes the programmable prescaler 375 as well as the voltage controlled word memory (RAM) discussed above. The illustrated word adjust and select bus 501 can separately access and adjust all voltage control words in the voltage control word memory RAM. When addressed, its voltage control word memory is connected to DA converter 320 via bus 511. The D / A converter 320 is connected to the oscillator OSC so that power is used under the microprocessor control via the lead DPWR via the sample hold circuit SH. Through the directional coupler 370 the jamming signal output of the oscillator OSC is fed back to the microprocessor 300. In fixed prescaler 376, the high frequency output is divided by a fixed divided coefficient. The split jamming frequency output is the output to the programmable prescaler 375. Programmable prescaler 375 is under control of microprocessor 300. In response to the premium channel frequency data sent from the headend to microprocessor 260 in FIG. 2, microprocessor 260 is sent to microprocessor 300 via a serial peripheral interface bus (FIGS. 2, 3). The data is divided in order by elements and time between count data to be transmitted. The microprocessor 300 programs what is divided by the elements of the programmable prescaler 375 via the read 502 and receives the added frequency output of the programmable prescaler via the read 503. The microprocessor 300 then counts the output at the counter 335.

The provision of an application specific integrated circuit (ASIC) applied helps to miniaturize the subscriber module of FIG. 3 and alleviates the external memory requirements of the microprocessor 300 of the microprocessor 300. On the other hand, the need for a limited voltage control word memory in the circuit ASIC is such that if the energy consumption of the first oscillator is reduced, as described in more detail in FIG. 6, the microprocessor relocates the second oscillator addressable slot. 300) opportunities can be limited. Compared to the unique programmable prescaler of FIG. 3, a second or fixed prescaler is preferably provided when the frequency range of the jammed television spectrum extends into the hyper band.

In FIG. 6, one embodiment of a voltage controlled word memory having 64 memories for addresses 1-64 is shown. Each fourth memory location (1, 5, 9 ...) is defined as a voltage control word coupled to the first oscillator. For convenience in establishing the protocols f10, ... f1F discussed, reference is made to 16 frequency control words for the first oscillator OSC1 and numbered from 0-F to hexadecimal. Referring to the circuit (ASIC) memory requirements described above, sixteen memory slots are permanently coupled to oscillator OSC1, but this design limits the voltage control words that are actually freely located in other oscillators.

The voltage control word is sequentially entered into the voltage control word memory of each oscillator used for jamming. First, all four oscillators will be used to jam each of the four premium channels. As will be described below, it is assumed that the subscriber is granted without receiving a premium channel, and in addition, it is assumed that all premium channels are disturbed at the same four jam coefficients.

In this example, sixteen voltage control words can fit in each oscillator memory and each of the four similar control words is associated with one premium channel frequency that is jammed. Thus, four groups of four similar control words enter 16 memory locations or type slots 1, 5, 9, 13, ... 61 of oscillator OSC1. This is represented by f10 to f1F. In a similar manner, sixteen voltage control words enter memory locations 2, 6, 10, ... 62 of oscillator OSC2. The sixteen voltage control words then enter memory locations 3, 7, 11, 15 ... 63 of oscillator OSC3 and are denoted by f30 ... f3F. Finally, the 16 voltage control words enter memory locations 4, 8, 12, 16 ... 64 of oscillator OSC4 and are labeled f40 ... f4F.

The adjustment algorithm for loading the first 10-bit voltage control word f10 into the first memory location 1 for the first oscillator OSC1 will be described in more detail. The division by the first programmable element from the download frequency data of the microprocessor 360 is transmitted via the read 502 to set the programmable prescaler 375. The energy consumption of all other oscillators OSC2-4 is reduced via lead OPWR2-4, and the energy consumption of oscillator OSC1 is reduced in FIG. Shown).

From the premium channel frequency data a first 10-bit voltage control word f10 is stored by the microprocessor 330 via bus 501 to a memory location 1 representing the first best estimate of the jamming frequency. . This word is passed to a digital-to-analog converter 320 which is converted into an analog voltage. The analog multiplexer (not shown in FIG. 5) selects the lead FREQ1 from the multiplexer to the oscillator OSC1. As a result, the analog voltage output of the digital-to-analog converter is provided to the sample hold circuit SH or 337 applied to the oscillator OSC1. Signal combiner 365 (not shown in FIG. 5 for simplicity) only passes a jamming signal from oscillator OSC1 to directional coupler 370, which reduces the energy consumption of all other oscillators OSC2-4 at this time. Because. Via the directional coupler 370, the jamming signal output is provided to a fixed prescaler 376. The fixed prescaler 376 divides the output frequency of the generator OSC1 by the first frequency. In accordance with the division by the element loaded into the programmable prescaler 375, the first frequency output of the fixed prescaler 376 is further divided into frequencies that can be counted as the counter 335 of the microprocessor 300. If it is recognized that the oscillator output frequency is hundreds of MHz and the clock for the microprocessor 300 operates only at 4 MHz, the frequency provided through the leads 503 must be effectively partitioned to accurately count. Since the fixed time between counts relates to the microprocessor 300 downloaded from the microprocessor 260, the counter 335 counts the frequency input on the read 503. As a result, the count is compared with the expected count, so the microprocessor adjusts the control word. As a result, the microprocessor 300 repeatedly inserts the algorithm until the voltage control word stored in the memory reflects the premium channel frequency as accurately as possible. Thus, this process is repeated four times so that the frequencies of the four premium channels are jammed by the oscillator (OSC).

In the process of loading the frequencies of the four premium channels of a special oscillator into the voltage control word memory, there are two additional designs in which the four voltage control words for a single premium channel can be intentionally changed. In the first minor design through the headend 100, four different frequencies may be intentionally selected with respect to one premium channel. Due to the 50 KHz resolution provided by the least significant bit position of the 10-bit voltage control word, the four different frequencies have a headend 100 in some range within 100 KHz to 250 KHz on the premium channel video carrier for the most effective premium channel jamming. Can be selected by. In a second minor design, the microprocessor 300 may be programmed to intentionally change the embedded voltage control word to be at approximately an expected download frequency, such as 50 KHz above or below an expected frequency. As a result, when the headend selects a single frequency for the first premium channel, such as 200 KHz on the video carrier, the voltage control word enters the memory equivalent with a 150 KHz video carrier of 200 KHz and 250 KHz. Interference of the two collaborative designs violates attempts to notch jamming signal frequencies that are intentionally changed by these designs.

The jamming element involves loading 16 voltage control words into the voltage control word memory for a particular oscillator. Jamming elements are selected for each premium channel and delivered globally from the headend. When four premium channels are jammed by each of the four oscillators OSC1-4 and jammed in the same jamming interval, each has four jamming elements. If the subscriber subscribes to all four premium channels coupled to oscillator OSC1, the energy consumption of oscillator OSC1 is reduced and there is no voltage control word going into memory when calibrating the oscillator. If the subscriber subscribes to two of the four channels, the microprocessor places the 16 channel words of the first oscillator such that the two unauthorized premium channel frequencies are jammed. As a result, the microprocessor places each of the eight control words to jam two unlicensed premium channels, automatically increasing the jamming interval and jamming depth according to the given reduction level and jamming factor of the premium program license. The jamming elements are intentionally selectable, at high levels, such as 8 for one particularly sensitive program on two different channels jammed by the same oscillator arranged in four respective jam coefficients, the sum of these jam coefficients being Equal to the maximum value of the voltage control word coupled to the oscillator (such as 16 in this example).

As mentioned above, each oscillator has a plurality of time slots arranged at various jamming frequencies of the particular oscillator assigned to the jam. Preferably, there are 16 time slots / cycle in each time slot corresponding to the same duration of time. In a novel aspect of the invention, the stall time (the time of a particular channel is jammed every cycle) is variable. Additionally, the number of time slots per cycle allocated to a particular channel may be changed.

For example, certain oscillators have 16 time slots / cycle and each time slot has a dead time of approximately 50 ms. This provides jamming in equal amounts to each channel coupled to the oscillator. For example, it is desirable to jam more than more channels than other channels to improve the jam coefficient for that channel. This increases the security for the channel choosing the increasing jam factor. For example, a subscription channel and an adult entertainment channel are more securely provided than any other premium channel. For illustrative purposes, some examples of how the stagnation time and time slots are changed by the oscillator when four jam channels are considered to be A, B, C, D are described below, for example, where channel A is a subscription fee. Channel, channel B is an adult entertainment channel, and channels C and D represent a premium channel.

8A shows a jamming pattern in which each channel A, B, C and D are arranged in the same sequential manner. If desired, most security is provided to channel A, most security to channel B, and the amounts for channels C and D are the same, the number of time slots assigned to a particular channel is varied as shown in Figure 8b. . Thus, channel A has a jam factor of about 50% (8/16) because it enables more security for channel A. Channel B has a jam coefficient of about 25% (4/16) when each channel C and D has a jam coefficient of about 12.5% (2/16). This jam coefficient is useful for illustration while ignoring the transition time between time slots.

It is noteworthy that the same jam coefficient is implemented by the shapes shown in FIGS. 8C and 8D. In addition, the joins for two or more of these shapes are used to arbitrarily change the pattern to maintain the same jam coefficient in order to disrupt the intrusion of the signal by the intruder.

Note that these jam coefficients change the number of time slots and simultaneously change the duration of each slot. For example, with respect to FIG. 8C, eight time slots are assigned to a first time slot having a duration of 4T, a second time slot having a duration of 2T, a third slot having a duration of T, and a duration of T. FIG. And the fourth, fifth, sixth, seventh, and eightth time slots are composed of 4T, 2T, T, and T, respectively. T is preferably 30-100 mm 3. The amount of time allocated for jamming a given channel is referred to as the dead time. Therefore, this stagnation time can be varied in various ways as shown in FIGS. 8A-8D. Information about the dead time and the order in which the channels are jammed may be changed periodically by the headend operator. For example, it is desirable to be able to jam some channels throughout the day rather than in a week.

Since the voltage control words are read from the memory or written to the memory and read in any order that is not particularly constant, the intruder will have any known order for proper time notch filtering. For example red (f11-f14) is the frequency of four premium channels to be jammed by oscillator OSCI. Addresses 1, 5, 9 and 13 store voltage control words for each of f11, f12, f13 and f14, respectively. However, the next four addresses 17, 21, 25, 29 store the voltage control words in a different order, for example, f14, f13, f12, f11, respectively. This order is changed at the remaining eight addresses, and when the voltage control word is applied to the oscillator (OSCI) in the normal operating mode, the output frequency of the jamming signal is changed in any order of the data entry.

The adjustment mode is inserted in the 64 voltage control words in the voltage control word corresponding to the desired jamming signal frequency in the initial turn-on generator. Periodically, the subscriber module enters the coordination mode to update the control word for deviations due to oscillator or digital-to-analog converter operation. It is desirable to remain within 50 KHz of the selected frequency, thus confusing the violation. As also noted, the periodically executed calibration mode is a high frequency that amplifies 4 KHz in normal operation than possible conventional frequency control methods such as phase locked loops. The coordination mode requires a second part, but television information is obtained in a television receiver tuned to a premium channel that does not permit.

Referring to FIGS. 6 and 7 with respect to the schematic block diagram of FIG. 3, the normal mode in operation is described below. First, in FIG. 3, when inserting the normal operation mode, the microprocessor 300 causes the first voltage control word stored in the memory address 1 of the voltage control word memory of FIG. 6 to be transferred to the oscillator OSCI. . D / A converter 320 converts 10-bit word 0010110101 to an analog voltage level. Under the control of the bit select bus, the analog multiplexer 330 selects read FREQ ₁ to transmit an analog voltage signal that is stored and held by the sample and hold circuit 337. All generators (OSCI) provide a jamming signal frequency output FREQ ₁ that matches the analog voltage signal provided past the analog multiplexer 330.

In Fig. 7, a normal operation mode is shown in the form of a timing block diagram, for example for purposes of description. The output of the D / A converter shows the analog voltage level representing the frequency (FREQ) for the oscillator (OSCI) at time t ₀ . Also shown is that analog multiplexer 330 connects A / D converter 320 to oscillator OSCI during time interval t ₀ -t ₁ . When the analog multiplexer is connected to the oscillator (OSCI) for a duration t ₀ -t ₁ , the applied analog voltage is stored and maintained for the duration t ₀ -t ₄ . Thus, it is shown that the output of oscillator OSCI is continuously applied at time t ₀ -t ₄ .

Under control of microprocessor 300 past lead OSSW1, switch 361 is simply opened and immediately closed when frequency FREQ ₁ is set at the output of oscillator OSCI. Switch 361 is closed yarn for a duration when the output of oscillator OSCI is amplified from frequency FREQ ₁ to FREQ ₂ . Before time t ₄ , switch 361 is opened again according to signal OSSW1. The jamming signal output of the oscillator 341 can be simply prevented.

At time t ₄ , D / A converter 320 is signaled to change the output frequency of oscillator OSCI to frequency FREQ ₂ . As described above, the analog multiplexer 330 refers to the analog voltage level as a gate and this time represents the frequency FREQ held in the sample and hold circuit 337. Thus, oscillator OSC2 provides an ice signal signal output that matches frequency FREQ ₂ by time t ₅ . During this time, the switch 261 which is simply opened before time t ₄ according to the switch control signal OSSW1 is closed again at a short time point after time t ₄ . There is a certain point during the normal mode of operation when one of the high frequency switches 361-364 is open, so that a portion of all jamming intervals are lost while the jamming signal is applied. When four premium program channel frequencies are jammed by a particular oscillator, each such period in the open state of a normally closed high frequency switch 361-364 corresponds to 5% of all intervals t ₀ -t ₆₄ (not shown). .

In a similar manner, the first frequency FREQ ₁ is executed by the oscillator OSC2 and referring back to FIG. 6, one can see the voltage control word 1010010110 provided to the oscillator OSC2 at the memory address 2. In FIG. 7, at time t ₁ , the analog voltage level is the output from the D / A converter 320 representing this word. At a time before time t ₁ , switch 362 is opened in accordance with signal OSSW2. Only frequency FREQ1 is set at the output of oscillator OSS2 or at time after time t ₁ and switch 362 is closed again in accordance with signal OSSW2 provided by microprocessor 300.

When the normal operation mode is continuous, all 64 memory allocations shown in FIG. 6 are addressed and provided for operating the oscillator OSC1-4. According to FIG. 7 only seven words are first shown as provided for selecting three frequencies for oscillator OSC1 and two frequencies for oscillator OSC2-4. However, the process for controlling all 16 frequencies for each oscillator varies in the order shown.

With respect to FIG. 7, it can be seen how the frequencies are output in any order to prevent intruders of the oscillator OSC1. The output frequencies FREQ1, FREQ2, FREQ3 and FREQ4 are output at intervals t ₀ -t ₄ , t ₄ -t ₈ , t ₈ -t ₁₂ and t ₁₂ -t ₁₆ , respectively. In the next interval, these frequencies are provided instead of successive FREQ4, FREQ3, FREQ2 and FREQ1. Thus, in the next consecutive interval, the frequency can be changed to FREQ3, FREQ4, FREQ1, FREQ2, for example. The frequency order applied during the last four consecutive intervals extending up to t ₄₈ -t ₆₄ can be changed back to, for example, FREQ3, FREQ4, FREQ1, FREQ2. Any order may be internally deployed in the microprocessor 260 of FIG. 2 or the microprocessor 300 of FIG. 3 or formed from the headend and embedded therein.

Claims (18)

An interdiction apparatus used in a cable television having a headend to prevent unauthorized reception of programming transmitted to a subscriber, comprising: jamming means for each jamming a plurality of unlicensed channels into a controlled jamming signal; Control means for controlling the jamming by a program during a jamming cycle in which the plurality of unlicensed channels are each jammed, the jamming means being determined by addressing communication from the headend to a control means; Selectively jamming each of the plurality of unlicensed channels with respect to the variable portion of the interdiction device. 2. The apparatus of claim 1, wherein the control means for determining the variable portion of the jamming cycle comprises: means for allocating a predetermined number of time slots per jamming cycle, and jamming at each frequency of the plurality of unlicensed channels for which selective jamming is desired; Means for allocating a variable number of time slots per cycle, wherein the variable number of time slots per jamming cycle assigned to each frequency of the plurality of unlicensed channels is controlled by addressing communication from the headend to a control means. An interaction device characterized in that it is determined. 3. The apparatus of claim 2, wherein the at least one unlicensed channel is assigned a larger number of time slots than the other unlicensed channels. 3. The apparatus of claim 2, wherein the means for assigning a particular time slot to a particular unlicensed channel generates a jamming pattern, wherein the control means changes the allocation of one or more time slots from one jamming cycle to the next jamming cycle. And the jamming pattern may be changed. The apparatus of claim 2, wherein the time slots have substantially the same period, and the amount of jamming per unlicensed channel for the jamming cycle is based on the number of time slots allocated to each channel in the jamming cycle. . 3. The method of claim 2, wherein the one or more time slots have periods that are not equal for other periods of the time slot, and the amount of jamming per unlicensed channel for jamming cycles is assigned to each unlicensed channel per cycle. Interaction apparatus based on the period of. 6. The apparatus of claim 5, wherein the period of each of said time slots ranges between approximately 30 and 100 ms. 6. The apparatus of claim 5, wherein the period of each time slot is approximately 50 ms. 7. The interaction device of claim 6, wherein the period of each of said time slots ranges from approximately 30 ms to approximately 100 ms. The apparatus of claim 2, wherein the allocation of a specific time slot to a specific channel generates a jamming pattern, and wherein the control means can change the jamming pattern. 7. A method according to any one of claims 3, 5 and 6, wherein the number of time slots per cycle and the period of one or more of the time slots assigned to a particular unlicensed channel are changeable and in a given jamming cycle. And the amount of time a particular unlicensed channel is jammed is based on the number and period of time slots assigned to the unlicensed channel for the given jamming cycle. A number of unlicensed in a cable television system having a headend and an control device with control oscillator means for generating a jamming signal that selectively intercepts each of the unlicensed channels during a jamming cycle consisting of a plurality of time slots. A method of changing the amount of time an unlicensed channel is jammed in the jamming cycle, wherein the jamming cycle selectively jams a channel, wherein the jamming cycle is determined by addressing communication from the headend to a control means. Assigning a variable number of time slots to each unlicensed channel, and interleaving the channel with the jamming signal for the variable portion of the jamming cycle based on the allocation of time slots per jamming cycle for each of the unlicensed channels. Jamming each of the unlicensed channels by dicing. Change the amount of time characterized in that a. 13. The method of claim 12, wherein each of the time slots has substantially the same period, and the amount of time that an unlicensed channel is jammed in a given jamming cycle is based on the number of time slots allocated to an unlicensed channel for the given jamming cycle. How to feature. 13. The method of claim 12, wherein the plurality of time slots do not all have the same period, and the amount of time that an unlicensed channel is jammed in a given jamming cycle is equal to a period of time slots allocated to an unlicensed channel for the given jamming cycle. Based method. 13. The method of claim 12, wherein the number of time slots assigned to any unlicensed channel and the period of one or more time slots are changeable, and the amount of time a particular unlicensed channel is jammed in a given jamming cycle is equal to the given jamming cycle. And based on the number and period of time slots assigned to the unlicensed channel for the channel. 16. A variable jamming pattern as claimed in any of claims 12, 13, 14, and 15, by varying the number of adjacent time slots assigned to any unlicensed channel in any given jamming cycle. And further comprising a step. 16. The method of any one of claims 12, 13, 14 and 15, further comprising generating a variable jamming pattern by changing the time slots assigned to any unlicensed channels in any given jamming cycle. Method comprising the as. An interdiction apparatus for use in a cable television having a headend to prohibit unauthorized reception of programming transmitted to a subscriber, comprising: means for interfacing a plurality of channels that require selective jamming using a controlled jamming signal; Control means for programmatically controlling generation of the jamming signal in response to an addressed communication from an end, wherein the intervention means selectively jamming the plurality of channels for each predetermined amount of time during a jamming cycle. The amount of time that any channel is jammed in a cycle can be programmatically, means for allocating a predetermined number of time slots per jamming cycle, and the plurality of time slots at frequencies in the channel that require selective jamming. Means for allocating at least one assigned to a particular channel The time slot is inter-prediction unit, characterized in that it does not occur continuously for the other time slots assigned to the particular channel.