Claims
- 1. A decoder for a pay-TV system comprising:
- receiver means for receiving a scrambled video signal, which signal comprises information codes relating to performances to be broadcasted, and for separating said scrambled video signal and said information codes;
- a separate card connectable to said receiver means;
- means for enabling a subscriber to select at least one information code corresponding to a performance which said subscribe desires to purchase; and
- wherein said receiver means comprises first microprocessor means for storing a plurality of said information codes, for transmitting to said card information codes selected by said subscriber and for transmitting to said card an enciphered descrambling code;
- wherein said card comprises:
- an EEPROM for storing at least credit information comprising an available amount of credit and said at least one information code selected by said subscriber; and wherein said card further comprises:
- second microprocessor means for comparing the cost of a performance selected by said subscriber with said available amount of credit when said selected performance is broadcast, and, if said cost is less than said available amount of credit, for deciphering said descrambling code and supplying said deciphered descrambling code to said first microprocessor, to thereby enable said first microprocessor to use said deciphered descrambling code to descramble said scrambled video signal and deliver it to a display unit.
- 2. The decoder according to claim 1, further comprising a pseudo-random generator and wherein said scrambled video signal comprises a plurality of lines and wherein said video signal is scrambled by permutation of said lines and further wherein said deciphered descrambling code controls said pseudo-random generator, further wherein said pseudo-random generator delivers input pointers for a table of a plurality of descrambling keys, each pointer selecting one of said descrambling keys for use in descrambling said scrambled video signal.
- 3. The decoder according to claim 1, further including a memory comprising a plurality of buffers, each buffer being capable of storing an entire line of said video signal, said descrambling key being used to store each arriving line in a specific buffer in order to output from said buffer a line previously stored therein and to display said outputted line.
Priority Claims (1)
Number |
Date |
Country |
Kind |
1576/86 |
Apr 1986 |
CHX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/488,493 filed Mar. 6, 1990, which in turn is a continuation of application Ser. No. 07/038,727 filed Apr. 15, 1987.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
8601962 |
Mar 1986 |
WOX |
Continuations (2)
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Number |
Date |
Country |
Parent |
488493 |
Mar 1990 |
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Parent |
38727 |
Apr 1987 |
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