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Multiplex interrogation system using pulses

  • US 4,067,008 A
  • Filed: 12/29/1975
  • Issued: 01/03/1978
  • Est. Priority Date: 12/29/1975
  • Status: Expired due to Term
First Claim
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1. In an interrogation and response system for monitoring the status of a plurality of protection zones of the type in which the protection zones are interrogated in sequence repeatedly by a series of interrogation signals, each sequential interrogation of all the protection zones constituting a complete sequential scan thereof, and reply signals are sequentially supplied according to the status of each protection zone in response to the respective sequential interrogation signals, the improvement comprising:

  • means for receiving said reply signals and generating for each of the protection zones a pattern of said reply signals for at least four of the most recent ones of said complete sequential scans of said zones; and

    means responsive to said reply signal patterns for determining and indicating therefrom the status of each particular protection zone, said zone status determining and indicating means indicating a change in status of one of said zones only when the entire pattern of the associated one of said reply signal patterns indicates a change in status whereby to substantially eliminate the effect of spurious signals on said system.

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