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Television receiver including a teletext decorder

  • US 4,912,555 A
  • Filed: 01/10/1989
  • Issued: 03/27/1990
  • Est. Priority Date: 01/11/1988
  • Status: Expired due to Fees
First Claim
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1. A receiver for television signal s including a teletext decoder circuit for decoding teletext signals constituted by character codes which are transmitted in the television signal, and comprising:

  • a video input circuit receiving the television signal and converting it into a serial data flow;

    an acquisition circuit for receiving the serial data flow supplied by the video input circuit and selecting that part therefrom which corresponds to the teletext page described by the viewer;

    a character generator comprising;

    a memory medium addressed by the character codes which together represent the teletext page desired by the user and which in response to each character code successively supply m2 series of m1 simultaneously occurring character picture element codes each indicating wether a corresponding picture element of the character must be displayed in the foreground colour or in the background colour;

    a generator circuit receiving a series of reference clock pulses and deriving display clock pulses therefrom;

    a converter circuit receiving each series of m1 simultaneously occurring character picture element codes as well as the display clock pulses for supplying the m1 character picture element codes of a series one after the other and at the display clock pulse rate;

    a display control circuit receiving the serial character picture element codes and converting each into an R, a G and a B signal for the relevant picture element of the character to be displayed;

    characterized in thatthe generator circuit is adapted to partition the series of reference clock pulses applied thereto into groups of N reference clock pulses each, in which N reference clock pulse periods correspond to the desired width of a character to be displayed, and to select from each such group m1 clock pulse to function as display clock pulses;

    the converter circuit is adapted to supply each character picture element code during a period which is dependent on the ordinal number of the character picture element code in the series of m1 character picture element codes.

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