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Line powered modem

  • US 4,592,069 A
  • Filed: 02/08/1984
  • Issued: 05/27/1986
  • Est. Priority Date: 02/10/1983
  • Status: Expired due to Term
First Claim
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1. An inductance simulation circuit to be connected to a transmission line providing a line-holding direct current and carrying alternating data signals, the circuit being operative to exhibit a relatively low resistance to direct current flow between two points in the circuit whereby a d.c. power supply for energising data handling apparatus can be derived from said direct current flow and to exhibit a relatively high impedance for alternating signals occuring between those points, the circuit comprising resistance means connected between the points, and an amplifier circuit connected across the resistance means to provide a low resistance d.c. path in parallel with the resistance means and operative to amplify the alternating signals and to apply the amplified alternating signals across the resistance means in a phase such that the amplifier circuit simulates an inductance connected across the points.

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