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Fail-safe digital phone

  • US 4,575,584 A
  • Filed: 07/05/1984
  • Issued: 03/11/1986
  • Est. Priority Date: 07/05/1984
  • Status: Expired due to Term
First Claim
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1. A fail-safe digital telephone set, operatively connected to a digital PBX having at least one digital telephone set operatively connected thereto, said digital PBX further operatively connected to at least one telephone line having an analog protocol, said digital PBX providing an interface to said telephone lines for each of said digital telephone sets and for said fail-safe digital telephone set in a normal operating mode, said fail-safe digital telephone set comprising:

  • (a) first means for providing digital communication of voice information with said digital PBX;

    (b) second means for providing analog communication of voice information with said telephone lines; and

    (c) switch means, having a first and a second terminal corresponding to a first and a second select position, respectively, said first means operatively connected to said first terminal and said second means operatively connected to said second terminal, for selecting between said first select position and said second select position in response to a control signal thereby causing said first means to be operative when said first select position is chosen and causing said second means to be operative when said second select position is chosen, to operatively connect said first means to said digital PBX in a normal operating mode and to operatively connect said second means to said telephone lines in a failure mode.

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