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Lockout device for preventing telephone eavesdropping from an extension device, and method

  • US 5,832,057 A
  • Filed: 05/23/1996
  • Issued: 11/03/1998
  • Est. Priority Date: 05/23/1996
  • Status: Expired due to Fees
First Claim
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1. A local communication coder for linking between a local telephone and a telecommunication system, and responsive to an in-coming wait signal from a cooperating remote communication coder linked to the telecommunication system, for enabling the local coder and the remote coder to encode and decode communications, and for locking out any cooperating extension communication coders linked to the telecommunication system from encoding and decoding communications, the local coder comprising:

  • wait means for advancing the local coder from a normal mode of operation during which out-going communications from the local coder are not encoded and in-coming communications to the local coder are not decoded, to a wait mode of operation during which the local coder listens for the wait signal from the remote coder;

    listen delay means responsive to the wait means for opening a listen window in the local coder to the remote coder as the local coder advances from the normal mode of operation to the wait mode of operation;

    listen means for detecting the in-coming wait signal from the remote coder during the wait mode to determine if the remote coder has advanced to the wait mode of operation;

    send means responsive to the listen means for opening a send window, and for sending an out-going wait signal to the remote coder indicating that the local coder has advanced to the wait mode of operation;

    lockout means responsive to the listen means and to the send means for advancing the local coder from the wait mode of operation to a code mode of operation during which the local coder and the remote coder are enabled to encode out-going communications and to decode in-coming communications, and for locking out any extension coders from the encoding and decoding;

    code means responsive to the lockout means for the encoding out-going communications from the local coder to the remote coder during the code mode, and for decoding in-coming communications to the local coder from the remote coder during the code mode.

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