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Communications system

  • US 6,377,589 B1
  • Filed: 03/19/1999
  • Issued: 04/23/2002
  • Est. Priority Date: 11/26/1996
  • Status: Expired due to Term
First Claim
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1. A method of operating a communications system including a telecommunications link between a remote terminal and a control station, the method comprising:

  • a) transmitting polling requests on a digital messaging channel carried on the telecommunications link, each polling request including a unique identifying code;

    b) generating at the remote terminal a poll response message and encrypting a part of said poll response message, the encrypted part of the poll response message including the unique identifying code for the polling request;

    c) returning a response signal from the remote terminal to the control station on the digital messaging channel; and

    d) decrypting the poll response message at the control station.

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