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Alarm system utilizing bidirectional wired television system

  • US 4,148,021 A
  • Filed: 09/07/1977
  • Issued: 04/03/1979
  • Est. Priority Date: 09/08/1976
  • Status: Expired due to Term
First Claim
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1. An alarm system utilizing a bidirectional wired TV system which is constructed to transmit a TV signal received by a community antenna to a central station and a plurality of subscribers'"'"' stations through a bidirectionally transmissible line interconnecting said central station and said plural subscribers'"'"' stations, wherein:

  • said plurality of subscribers'"'"' stations are each provided with alarm signal generating means operative to generate a low frequency alarm signal representative of any emergency condition, a first carrier wave generator operative to generate a first carrier wave signal having a predetermined frequency higher than that of the alarm signal, and a modulator coupled with said alarm signal generating means and first carrier wave generator to modulate said first carrier wave signal with said alarm signal;

    said central station is provided with a demodulator operative to receive and demodulate the modulated alarm signal transmitted from that of said plurality of subscribers'"'"' stations which is generating the alarm signal through said bidirectionally transmissible line, a first alarm signal identifying means coupled to said demodulator for identifying the emergency condition represented by the demodulated alarm signal from said demodulator, a second carrier wave generator operative to generate a second carrier wave signal having a predetermined high frequency different from that of said first carrier wave signal and a remodulator coupled to said demodulator and second carrier wave generator for remodulating the second carrier wave signal with the demodulated alarm signal from said demodulator; and

    at least one of said plurality of subscribers'"'"' stations is further provided with a redemodulator operative to receive and remodulate the remodulated alarm signal from said remodulator through said bidirectionally transmissible line, and a second alarm signal identifying means coupled with said redemodulator to identify the emergency condition represented by the redemodulated signal from said second demodulator.

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