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Two-wire, multiple-transducer communications system

  • US 4,093,946 A
  • Filed: 03/01/1976
  • Issued: 06/06/1978
  • Est. Priority Date: 03/01/1976
  • Status: Expired due to Term
First Claim
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1. A system responsive to data request signals for retrieving data from a selected one of a plurality of data gathering devices remotely located and connected in parallel to a single cable, comprising:

  • an interrogator responsive to data request signals including;

    means for transmitting an address signal along the cable indicative of the particular data gathering device from which data is to be retrieved; and

    means for applying a constant signal to the cable after the address signal has been transmitted;

    one or more decoders each associated with a corresponding data gathering device and each including;

    means for comparing the address signal transmitted along the cable with an identification signal uniquely identifying the decoder to produce an enabling signal upon correspondence thereof for activating the corresponding data gathering device; and

    corresponding means responsive to the enabling signal for selectively connecting a low impedance across the cable conductors in response to digital data from the data gathering device;

    the digital data from the selected data gathering device being reproduced at the interrogator by detecting the variations in the signal level across the cable produced by the responding means.

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