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Data communication system

  • US 5,617,282 A
  • Filed: 02/25/1994
  • Issued: 04/01/1997
  • Est. Priority Date: 03/02/1993
  • Status: Expired due to Term
First Claim
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1. A data communication system, comprising:

  • a bus system which includes a symmetrical transmission line having first and second conductors, and an ohmic load impedance connected between the first and second conductors, the load impedance having a center tap; and

    a protective circuit having a current-voltage characteristic, the protective circuit being connected between the center tap of the load impedance and a reference potential, the protective circuit including means for dividing the current-voltage characteristic into regions depending on the voltage across the protective circuit, the regions of the current-voltage characteristic includinga first region in which no current flows through the protective circuit when the voltage across it is below a threshold voltage, the threshold voltage being higher than a normal voltage on the transmission line during data communication,a second region in which current through the protective circuit rises steeply with increasing voltage when the voltage across the protective circuit is between the threshold voltage and a knee voltage, anda third region in which current through the protective circuit is limited when the voltage across it is above the knee voltage.

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