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Analog self-test circuitry for a trunk interface

  • US 5,761,273 A
  • Filed: 12/27/1995
  • Issued: 06/02/1998
  • Est. Priority Date: 12/27/1995
  • Status: Expired due to Term
First Claim
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1. A self test circuit, coupled to controlling circuitry which generates a test signal, for a trunk interface, comprising:

  • a timer/counter circuit for receiving the test signal from said controlling circuitry and generating a selection signal, the selection signal indicating a test mode or a normal operation mode;

    a multiplexer circuit for receiving and outputting simulated tip and ring signals responsive to the selection signal when in the test mode;

    switching circuitry, responsive to the selection signal, for receiving and outputting a tip signal and a ring signal when in the normal operation mode and the simulated tip and ring signals when in the test mode, wherein the tip and ring signals received by said switching circuitry have been divided down by a voltage divider circuit; and

    detection circuitry, coupled to said switching circuitry, for detecting a state of the tip and ring signals during the normal operation mode and detecting a state of the simulated tip and ring signals during the test mode, wherein during the test mode said controlling circuitry receives the detected states of the simulated tip and ring signals.

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