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Alarm system utilizing a bidirectional transmission line in CATV system

  • US 4,066,966 A
  • Filed: 04/15/1976
  • Issued: 01/03/1978
  • Est. Priority Date: 03/30/1976
  • Status: Expired due to Term
First Claim
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1. A subscription alarm system having locations in group units, utilizing a bidirectional transmission line of a wired television broadcasting system, said system employing a plurality of alarm signal generators located at the subscribers'"'"' locations, generating low frequency alarm signals of frequencies common to the respective group units, said frequencies being different for subscribers in given respective group units, each of said alarm signal generators being provided for each subscriber including:

  • modulator for each of said respective group units, for modulating the low frequency alarm signals of said alarm signal generators with different high frequency carrier signals;

    a receiving means coupled to the respective modulators through said bidirectional transmission line, for receiving said modulated alarm signals, said receiving means comprising frequency converting means for converting modulated alarm signals transmitted from said modulators into signals having lower frequencies than the carrier frequencies of said modulated alarm signals,a plurality of band-pass filters for dividing said modulated alarm signals from said frequency converting means into modulated alarm signals for respective subscriber groups,a plurality of detectors for demodulating said modulated alarm signals from said band-pass filters and extracting therefrom alarm signals for respective subscriber groups,a plurality of resonators for separating an alarm signal for each subscriber from said alarm signals of said detectors, anda plurality of alarm indicators for responding to each alarm signal from each of said resonators.

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