Two mode scrambling system using identifier pulse in vertical blanking interval
First Claim
1. A television system comprising:
- means for supplying television signal transmissions selectively encoded in one of two different formats A and B;
means supplying market code information on one of two horizontal lines in the vertical intervals of said television signal transmissions;
means for receiving said television signal transmissions and said market code information;
means developing an identifier pulse from said market code information; and
format mode means including a decoder A and a decoder B responsive to said identifier pulse for selectively decoding said television signal transmissions, the selected one of said two horizontal lines bearing said market code information in the vertical blanking interval of the television signal transmission determining whether the television signal transmission is encoded in format A or in format B.
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Accused Products
Abstract
A cable television system capable of decoding signals encoded in two different formats, A and B. Format A is identified by digital data on horizontal lines 10-13 in the vertical blanking interval and format B by digital data on horizontal lines 14-17 in the vertical blanking interval. Logic circuitry receives the vertical blanking interval data and supplies one pulse marking the beginning of the vertical blanking interval and an identifier pulse derived from digital data on horizontal lines 13 or 17. A format mode control switch includes a monostable timing circuit producing an output responsive to the vertical blanking interval pulse for a period terminating at approximately horizontal line 14. The timing circuit output is supplied along with the identifier pulse to the inputs of a flipflop for determining which of the decoders A and B is to be energized.
116 Citations
5 Claims
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1. A television system comprising:
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means for supplying television signal transmissions selectively encoded in one of two different formats A and B; means supplying market code information on one of two horizontal lines in the vertical intervals of said television signal transmissions; means for receiving said television signal transmissions and said market code information; means developing an identifier pulse from said market code information; and format mode means including a decoder A and a decoder B responsive to said identifier pulse for selectively decoding said television signal transmissions, the selected one of said two horizontal lines bearing said market code information in the vertical blanking interval of the television signal transmission determining whether the television signal transmission is encoded in format A or in format B. - View Dependent Claims (2, 3, 4)
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5. A cable television system comprising:
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means for transmitting television signals encoded in a selected one of two different formats A and B, all of said television signals including market code information on one of two different horizontal lines in the vertical blanking intervals, with the horizontal line position of said market code information in said intervals determining said format A and said format B; a decoder A and a decoder B for selectively decoding signals encoded in said formats A and B, respectively; means for generating, from said market code information, an identifier pulse; means for receiving said transmitted television signals and for determining, from said identifier pulse, the position of said market code information in the vertical blanking interval, said means including timing means initiated at the beginning of the vertical blanking interval and ending at a time in the vertical blanking interval occurring between said two different horizontal lines; means for determining coincidence between operation of said timing means and occurrence of said identifier pulse; and a format mode switch for selectively energizing decoder A and decoder B as a function of said coincidence.
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Specification