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Monitoring system and method utilizing signal injection for determining channel reception of video receivers

  • US 4,425,578 A
  • Filed: 01/12/1981
  • Issued: 01/10/1984
  • Est. Priority Date: 01/12/1981
  • Status: Expired due to Term
First Claim
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1. Apparatus for determining the video channel of a plurality of predetermined channels to which a video receiver is tuned, said video receiver including a signal input for the video channel carrier signals of said predetermined channels, channel selection and tuning apparatus, and a video circuit, said apparatus comprising:

  • signal source means being selectively controllable and coupled to said signal input of said video receiver for generating one of a predetermined plurality of signal frequencies in a predetermined frequency set, each of said signal frequencies in said predetermined frequency set corresponding to one of said predetermined channels tuned by said video receiver and defined by a predetermined offset frequency fr from each of said channel frequencies;

    means for controlling said signal source generating means; and

    means responsive to said video receiver for detecting a predetermined detection frequency signal fr resulting from the combination of the signal generated by said signal source generating means and the video carrier signal corresponding to the channel to which said video receiver is tuned,said signal source controlling means comprising means for advancing said signal source generating means to generate successive ones of said signal frequencies at predetermined time intervals.

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