A SUBSCRIBER VIDEO-TV SYSTEM

Abstract: A video-TV subscriber system providing one or more channels from a video recording means including: (a) a radio frequency signal scrambling means comprising a scrambling means (31), the output thereof being combined with an RF signal having at least one channel of transmitted information carried at a prescribed frequency, wherein the scrambling means includes a selectively operable signal generator to produce an output signal at approximately the carrier frequency of a channel of the RF signal and unsynchronized with the carrier wave form of said channel; (b) a key monitoring means for monitoring the presence of a key within a key module (51), wherein said key controls the operation of said generator, comprising: (i) at least one key station (54) to accomodate a key; (ii) an addressing means to access said station periodically; (iii) an input sensing means to sense the presence of a key addressed by the addressing means; (iv) a master control means (53) to control the addressing means and sensing means, and to process information acquired from said sensing means; and (v) interface means (59) to facilitate the operation of the master control means, wherein a station (54) includes a decoding means (52) to decode a correctly coded key accomodated therein and indicate the status of said station to the sensing means.

Description: "A Subscriber Video-TV System" THIS INVENTION relates to a video - TV subscriber system for providing subscribers thereto with means for viewing a particular channel on a television receiver wherein the channel would normally contain unintelligible information, and for providing means for monitoring the periods of use by subscribers of the system. Moreover, the invention relates to a device for selec¬ tively unscrambling a previously scrambled channel of in¬ formation, wherein the information is derived from a video cassette player for ultimate viewing upon a number of television receivers within a hotel, motel or the like, and a computerized monitoring network for monitoring the use of a key which is used by a subscriber to enable or disable the scrambling device. The invention finds particular application in the field of user-pay-video subscription in that a video recording from a video cassette player may be combined with a conven¬ tional TV signal and displayed upon a particular channel on a number of television receivers within a hotel, for example. The video recording on the particular channel would normally be scrambled so that a user of the tele¬ vision receiver may view the normal TV channels without difficulty but would not be able to view the channel displaying the video recording with any coherency, unless he was able to disable the scrambler. Means of disabling the scrambler are provided by way of a key which must be purchased or hired from the authority controlling the video recording. Further the invention provides computerized means for accounting the periods of time for when keys have been removed from a key storage module location. OMPI In one form the invention resides in a video - TV subscri¬ ber system for selectively providing one or more channels of information within a transmitted signal for ultimate viewing on a television receiver by a subscriber thereto, said information being derived from a video recording means, and a subscriber monitoring means for providing an account of the transactions made by subscribers to the system; wherein the video - TV subscriber system includes a radio frequency scrambling means and a subscriber moni- toring means. In another form the invention resides in a radio frequency signal scrambling means comprising a scrambling means, the output thereof being combined with an RF signal having at least one channel of transmitted information carried at a prescribed frequency, wherein the scrambling means in¬ cludes a selectively operable signal generator which is adapted to produce an output signal at approximately the carrier frequency of a channel of the RF signal, and said output signal being unsynchronized with the carrier wave form of said channel. According to a preferred feature of the invention the radio frequency scrambling means includes a control means adapted to control the operation of the signal generator in accordance with the use of a. ey therewith. According to another preferred feature of the invention the key is characterized by a code identifiable with the control means and the control means comprises a key decod¬ ing means and a switching means wherein the key decoding means is adapted to receive a key, decode the said key and provide a resultant control signal to the switching means, the switching means being adapted to receive the said con¬ trol signal and disable or enable the operation of the said generator in accordance with the control signal. PREACH OMPI ι ∞ In another form the invention resides in a key monitoring means for monitoring the presence of a key within a key module, comprising:- (i) at least one key station adapted to accommodate a key; (ii) an addressing means adapted to access said key station periodically; (iii) an input sensing means adapted to sense the presence of a key addressed by the addressing means; (iv) a master control means adapted to control the operation of the addressing means and input sensing means, and to process information acquired from said input sensing means; and (v) interface means adapted to facilitate the opera¬ tion of the master control means, wherein a key station includes a decoding means to decode a correctly coded key accommodated therein and to provide an indication of the status of the said station to the input sensing means upon access thereto. According to a preferred feature of the invention; the key monitoring means is a computer, and communication with the computer is conducted through the input and output ports thereof. The invention will be better understood by reference to the following description of several embodiments thereof. The description is made with reference to the accompanying drawings wherein:- Fig. 1 is a block diagram of a video - TV subscriber system embodying a radio frequency scrambling means in accordance with the first embodiment of the in vention; Fig. 2 is a block diagram of a video frequency scram¬ bling means in accordance with the first embodiment of the invention; Fig. 3 is a circuit diagram of a radio frequency scrambling means in accordance with the first embodi¬ ment of the invention; Fig. 4 is a block diagram of a video - TV subscriber system embodying a radio frequency scrambling means in accordance with the second embodiment of the in- vention; Fig. 5 is a block diagram of a radio frequency scram¬ bling means in accordance with the second embodiment; Fig. 6 is a block diagram of a video - TV subscriber system embodying a key monitoring means in accordance with the third embodiment of the invention; and Fig. 7 is a circuit diagram of a key monitoring means in accordance with the " third embodiment of the inven¬ tion. The first embodiment is directed towards a means of selec- tively scrambling a video signal produced by a video cas¬ sette player which has been combined with a TV signal for receipt by a number of television receivers. With reference to Fig. 1 of the drawings a video informa¬ tion signal is produced at a source 11, being a video cassette player and is transmitted ultimately to a number of television receivers 12 at a prespecified carrier frequency for viewing on a particular channel . The video information signal is initially transmitted along a trans¬ mission line 13 at a prespecified carrier frequency and is conditioned by means of an RF amplifier 14 for acceptance into a combination network 15. The combination network 15 combines the RF video information signal with the standard RF TV information signal, usually received via a conven¬ tional receiving TV antenna 17 along a transmission line 16, such that a resultant RF signal is produced for fur¬ ther transmission along line 18. This resultant RF signal is subsequently amplified by a second RF amplifier 19 for acceptance into a splitter network 20. The splitter network 20 essentially divides the resultant RF signal into a number of identical input signals and conditions these input signals for reception by the television re¬ ceivers 12 along input transmission lines 30 and via signal scrambler-decoder units 31. In some applications of the described TV - video subscri¬ ber system, it may be necessary to isolate respective input signals from the spurious effects of feedback and reflected RF signals derived from adjacent input transmis¬ sion lines 30. Hence it may be necessary to include an isolation network into each of the input transmission lines 30. Referring to. Fig. 2 of the drawings, a single input signal is transmitted along its individual transmission line 21 to an isolation network 22. The isolation network 22 comprises a matched RF amplifier 23 and a signal attenua¬ tor 24 which combine to initially raise the signal level by approximately 18 dB and subsequently lower the signal level by 18 dB. This action provides sufficient isolation of an input signal from other input signals such that spurious line effects which may be incurred by the system are effectively eliminated. The isolated signal from the isolation network 22 is then combined with the output of the signal scrambler-decoder unit 25 by way of another combination network 26 whereupon the resultant signal is received by the television receiver 29. In some cases, the signal alternator 24 is not necessary due to high isolation levels between adjacent rooms. As shown in Fig. 3, the signal scrambler-decoder unit 31 comprises a key decoder circuit, shown generally at 27, and an oscillator circuit, shown generally at 28. The key decoder circuit may be preset to receive a singu¬ larly coded key 34 in order to control operation of the oscillator circuit. A series of resistors 32, each cha¬ racterized by different respective resistance values, are connected via an eight pole dip switch 33, to form one branch of a voltage divider network 49. The other branch of the network is defined when a coded key 34 is inserted into the key receiving socket 35 of the signal scrambler, the key itself containing a resistive component which completes the circuit of the divider network. The output 38 of the voltage divider network is applied to the res¬ pective inverting input of a first comparator 36 and the respective non-inverting input of a second comparator 37. Prespecified resistors 39 and 40 combine to form two separate secondary voltage divider networks which, when applied respectively to the non-inverting input of the first comparator 36 and the inverting input of the second comparator 37, provide a reference signal with a specified tolerance to which the output 38 is compared. The outputs of the comparators are connected via resistors 41a and 41b to the base of a pnp transistor 42. The output of the transistor 42, taken from the collector thereof, is con¬ nected by way of an RF choke 43 to the input of a Colpitt's Oscillator circuit shown generally at 44. A zener diode 45 is included to stabilize the voltage to the oscillator circuit. The oscillator 44 is tuned to provide an output sine wave at approximately the carrier frequency of the channel containing the video information transmitted within the previously described isolated RF signal which is input to a television receiver. The output connectors 46 is iso- OMPI lated from the input connector 46' by a hybrid RF isola¬ tion amplifier 47 and the DC supply is from RF transcience by a second RF choke 48. Now describing the operation of the signal scrambler-deco¬ der unit 25, the output of at least one of the comparators 36, 37 will normally be low when there is an imbalance in the voltage divider network 49 which is sufficient to provide a voltage output beyond the bounds of the toler¬ ance of the reference signal specified by the aforemen- tioned secondary voltage divider networks. Accordingly, the base-emitter junction of the transistor 42 will be forward-biased and hence the collector output signal will be high. This high signal is sufficient to effect opera¬ tion of the oscillator circuit whereby the signal output therefrom will be applied to the isolated RF signal by way of the combination network 26. As the output signal generated from the oscillator circuit is not synchronized with the video information signal, and the frequency of the generated output signal is approximately the same as the carrier of the video information signal , interference and distortion of the channel containing the video infor¬ mation signal will result. When the voltage divider is balanced such that the output voltage therefrom falls within the bounds of the tolerance of the reference signal, the output of both comparators 36 and 37 will be high. Hence the transistor 42 will turn off, thereby providing a low voltage at its collector output terminal. Consequently, this low voltage is suffi¬ cient to switch the Colpitt's Oscillator 44 off and hence no output signal therefrom will be input into the combina¬ tion network 26. Thus eliminating the previous distortion effect of the isolated RF signal. As can be seen, control of the signal scrambler-decoder unit 25 is facilitated by the use of a coded key 34, whereby use of a key characterised by a resistance which matches the preset resistance specified by the DIP switch 33, will effectively eliminate the distorting influence of the oscillator circuit upon the isolated RF signal. The distortion (when present) of the isolated signal will only appear on the channel containing the video informa¬ tion signal within the said isolated signal, hence the remaining channels containing standard TV information signals will be unaffected. Thus when the oscillator is enabled, coherent viewing through the television receiver of the channel displaying the video signal is virtually impossible due to the interference effect of the oscilla¬ tor generated signal upon the video signal, whilst viewing of other channels displaying the TV signal will be un¬ affected. According to a second embodiment of the invention, as shown in Fig. 4, two video players 101 and 102 produce separate video information signals which are transmitted along transmission lines 103 and 104 respectively at dif¬ ferent prescribed carrier frequencies to a combination network 105. The combination network 105 combines the two transmitted video information signals with a conventional television signal which has been transmitted to the net¬ work 105 via a main transmission line 106 so as to provide two further channels of transmitted information for view¬ ing by a subscriber upon a television receiver. This combined RF signal is transmitted along the line 107 to a splitter network 108 as described in the previous embodi¬ ment. The splitter network divides the applied combined signal into identical input signals for transmission along lines 112 to a series of television receivers 109. The outputs of respective scrambler decoder units 110 are with the transmitted input signals, shown generally at 115, prior to reception by the receivers 109. The scrambler decoder unit 110 comprises a key decoder circuit 113 and first and second oscillators 114 and 115 respectively. The key decoder circuit 113 is adapted to control the operation of both oscillators which combine to provide the output signal of the scrambler decoder unit 110. The first oscillator 114 is tuned to generate a signal at approximately the carrier frequency of one of the additional channels of the transmitted input signal and the second oscillator 115 is tuned to generate a signal at approximately the carrier frequency of the other additional channel. Each generated signal is unsynσhroni- sed with the transmitted input signal and hence, when present, distort the video information signal contained within the respective additional channels. The key de¬ coder circuit 113 is conditioned to selectively operate either oscillator upon the input of a correctly coded key thereto. The key decoding circuit being provided with means to select only one oscillator as determined by the coded key. That is each oscillator is matched with a singularly coded key. Thus it is possible to disable the distortion or interference effects of only one oscillator at a time. The third embodiment of the invention is directed towards a key monitoring system which is adapted to monitor the use of a number of coded control keys as described in the first and second embodiments. With reference to Fig. 6 of the drawings a key module 51 contains a series of key stations 54 arranged in banks of eight. Each station 54 is adapted to accommodate a coded key (not shown), and is defined to be located at a unique -SURE4 _ OMPI ^ address. A station is adapted to receive one and only one specifically coded key. A decoding circuit, collectively grouped at 52, is associated with each station 54 and is connected by way of a data/address bus 56 and interface circuit 59 to the input/output port 55 of a micro-computer 53. Communication to and from the computer with the outside world may be provided by way of a peripheral device 62, which may be a terminal or printer device. The data/address bus 56 and interface circuit 59, between the decoding circuits 52 of the key stations 54 and the micro-computer 53, is shown in more detail in Fig. 7. A series of input lines 65 from the decoding circuits of key stations 54 are connected in banks of eight to one of a series of eight input buffers 57 which are of the IC type designated 'LS240. Each buffer 57 is connected by way of buffer outputs 58 to a busline 63. The busline 63 is in turn connected to the input port of the micro-computer by way of data lines 64. Successive stations 54 located within a bank are consecutively addressed by the micro-computer 53 through an output buffer 58 and an address decoder 61, which is of the IC type designated ' S138. The addressing technique involves the selection of an appropriate input buffer 57 containing data reflec¬ ting the status information of each key station located within the bank thereby. Consequently the data from this addressed bank is placed on the busline 63 and input to the micro-computer as described above. The status infor¬ mation which is input to the computer indicates whether a correctly coded key is present within a particular key station. The key module starting address is accomplished by the comparison of the state of a set of four address lines 67 output from the output port of the micro-computer 53, with the state of four preset reference lines 60. The reference lines being set by a bank of four DIP-switches SI, S2, S3, S4. The comparison is performed by a 4-bit magnitude comparator 68, which is of the IC type designa- ted 'LS85. Upon the successful comparison of these four address lines the address decoder 61 is enabled by way of line 66 and subsequently decodes three remaining address lines 67' output from the output port of the micro-compu¬ ter 53. The particular enable line 68 selected by the decoded address is used to enable the appropriate input buffer 57 by way of chip enable inputs 69. Now describing the operation of the overall concept of the key monitoring system, the micro-computer 53 is programmed to continuously monitor each of the key stations 54 con¬ tinuously and sense the presence of a corresponding cor¬ rectly coded key. Accordingly the time for which a coded key is present or absent from a key station is recorded within the memory of the micro-computer. Additionly, the micro-computer may be programmed to enter an alarm state upon the incorrect insertion or withdrawal of a coded key from its key station. Accordingly the micro-computer may provide an instruction procedure for the correct insertion or withdrawal of a coded control key from the key module. According to a fourth embodiment of the invention, the key monitoring system may be controlled by a computer network characterized by a master-slave type of arrangement. The master may be defined as a unit embodying the main key storage facility and the slave may be defined as a remote unit which only accepts the return of keys which have been previously withdrawn from the master. Further, the system may include a facility wherein a key must be returned to the main storage facility from the site of the slave within a prescribed time. According to a preferred feature of each of the above embodiments, the coded key is a jack plug and has its out¬ put impedance .characterized by the value of a resistance therein, which forms. an identifiable code for the key. •i It should be appreciated that the scope of the invention need not be limited to the particular scope of the embodi¬ ments described above and in particular need not be limi¬ ted to a key characterized by its impedance but may " in¬ clude any type of key. For example a key characterized by its shape whereupon insertion into a lock may enable or disable the signal scrambler. Or alternatively a key may be characterized by its magnetic properties and wherein a corresponding decoding means is utilized. In addition it should be appreciated that the invention could be applied to the use of more than two additional information channels, wherein the scrambler-decoder unit is adapted to provide more than two generated output sig¬ nals for scrambling the transmitted input signal. Accor¬ dingly the decoding means may incorporate facilities for decoding more than one key at a time and hence disable the operation of more than one signal generator at the same time. ^0R £ -4 OMPI_

Claims: THE CLAIMS defining the invention are as follows:- 1. A radio frequency signal scrambling means comprising a scrambling means, the output thereof being combined with an RF signal having at least one channel of transmitted information carried at a prescribed frequency, wherein the scrambling means includes a selectively operable signal generator which is adapted to produce an output signal at approximately the carrier frequency of a channel of the RF signal, and said output signal being unsynchronized with the carrier wave form of said channel . 2. A radio frequency signal scrambling means as claimed in claim 1, .wherein the scrambling means includes a con¬ trol means adapted to control the operation of the said signal generator in accordance with the use of a key therewith. 3. A radio frequency signal scrambling means as claimed in Claim 2, wherein the key is characterized by a code identifiable with the control means and the control means comprises a key decoding * means and a switching means wherein the key decoding means is adapted to receive a key, decode the said key and provide a resultant control signal to the switching means, the switching means being adapted to receive the said control signal and disable or enable the operation of the said signal generator in accordance with the control signal. 4. A radio frequency signal scrambling means as claimed in Claim 2 or Claim 3, wherein the key decoding means com¬ prises conditioning means and a comparator means, wherein the said conditioning means is adapted bo provide a con¬ ditioned signal indicative of the code of the key, to the comparator means, the comparator means being adapted to compare the conditioned signal with a predetermined refe- rence signal and provide a resultant control signal indi¬ cative of the comparison to the said switching means. 5. A radio frequency signal scrambling means as claimed in any one of Claims 1, 2, 3 or 4 wherein the signal generator includes an oscillator circuit which is tuned to the carrier frequency of the said channel, wherein the oscillator circuit is a Colpitt's oscillator. 6. A radio frequency signal scrambling means as claimed in Claim 4 or 5, wherein the said conditioning means com¬ prises a voltage divider network having a first branch preset to a specified impedance and a second branch formed to accommodate the said input key, wherein the code of the key defines an impedance within the second branch and the said conditioned signal is defined as the resultant divi¬ ded voltage of the network. 7. A radio frequency signal scrambling means as claimed in Claim 4 or Claims 5 or 6 as dependent upon Claim 4, wherein the said reference signal is derived from at least one secondary voltage divider network which is adapted to provide an upper and/or lower reference signal. 8. A key monitoring means for monitoring the presence of a key within a key module, comprising:- (i) at least one key station adapted to accommodate a key; (ii) an addressing means adapted to access said key station periodically; (iii) an input sensing means adapted to sense the presence of a key addressed by the addressing means; (iv) a master control means adapted to control the operation of the addressing means and input sensing means, and to process information acquired from said input sensing means; and (v) interface means adapted to facilitate the opera¬ tion of the master control means, wherein a key station includes * a decoding means to decode a correctly coded key accommodated therein and to provide an indication of the status of the said station to the input sensing means upon access thereto. 9. A key monitoring means as claimed in Claim 8, wherein the master control means is a computer, and communication with the said computer is conducted through the input and output ports thereof. 10. A key monitoring means as claimed in claim 8 or 9 wherein the master control means includes the input sens¬ ing means and the addressing means. 11. A key monitoring means as claimed in Claim 10, where¬ in the interface means for facilitating the addressing means, includes an address label means such that the addressing phase may be instituted by the master control means uppn selecting the correct address label means. 12. A key monitoring means as claimed in Claim 10 or 11, wherein the interface means includes an address decoder, whereupon enabling the address decoder allows the master control to address a bank of key stations. 13. A key monitoring means as claimed in Claim 12, where¬ in the master control means addresses each key station sequentially within a bank of key stations and processes the status information contained therein, and subsequently addresses successive banks of key stations through the address decoder. 14. A video - TV subscriber system for selectively provi¬ ding one or more channels of information within a trans¬ mitted signal for ultimate viewing on a television recei¬ ver by a subscriber thereto, said information being deri¬ ved from a video recording means, and a subscriber moni¬ toring means for providing an account of the transactions made by subscribers to the system; wherein the video - TV subscriber system includes a radio frequency scrambling means as claimed in any one of Claims 1 to 7 and a sub¬ scriber monitoring means as claimed in any one of Claims 8 to 13. 15. A radio frequency scrambling means substantially as herein described with reference to the drawings. 16. A key monitoring means substantially as herein des¬ cribed with reference to the drawings. 17. A video - TV subscriber system substantially as herein described with reference to the drawings.

Inventors: IVACHEV ALEX, IVACHEV, ALEX
Applicants: IVACHEV ALEX, IVACHEV, ALEX
Application year: 1983
Main classification: H04K1
IPC codes: H04K1, H04N7