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Integrated modem and line-isolation circuitry and associated method utilizing a DC termination pin to monitor line voltage

  • US 6,771,696 B1
  • Filed: 06/26/2000
  • Issued: 08/03/2004
  • Est. Priority Date: 07/23/1999
  • Status: Expired due to Fees
First Claim
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1. A combined modem and line-isolation system, comprising:

  • a line-side line-isolation integrated circuit configured to be coupled to a phone line;

    a system-side line-isolation integrated circuit;

    digital signal processing (DSP) circuitry included within the system-side line-isolation integrated circuit, the DSP circuitry having a modem processor for modem data and a digital processor for system-side circuitry;

    a dc termination pin on the line-side line isolation integrated circuit, the line-side line-isolation integrated circuit configured to utilize the dc termination pin to provide proper dc termination characteristics to the phone line when the line-side line-isolation circuit is in an off-hook state;

    circuitry coupled to the dc termination pin and configured to cause a voltage at the dc termination pin to be proportional to a voltage on the phone line when the line-isolation integrated circuit is in an on-hook state; and

    circuitry within the line-side line-isolation integrated circuit coupled to the dc termination pin and configured to utilize the dc termination pin to monitor the voltage at the dc termination pin as a voltage representative of a voltage on the phone line when the line-side line-isolation integrated circuit is in an on-hook state, wherein the line-side line-isolation integrated circuit and the system-side line-isolation integrated circuit are capable of being coupled to an isolation barrier to communicate digital information with each other through the isolation barrier.

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