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Method of indicating a portable unit of a cordless telephone instrument out of operational area and its device

  • US 5,644,620 A
  • Filed: 05/26/1995
  • Issued: 07/01/1997
  • Est. Priority Date: 06/30/1994
  • Status: Expired due to Fees
First Claim
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1. A method of indicating that a portable unit of a cordless telephone instrument which comprises a fixed unit and a portable unit is out of operational area, comprising the steps of:

  • starting counting of a predetermined first reference time at said portable unit,transmitting a registration signal of a first frequency peculiar to said cordless telephone instrument from said portable unit after lapse of the predetermined first reference time and starting next counting of the predetermined first reference time by said portable unit;

    transmitting, upon reception of the registration signal by a fixed unit, a response signal of a second frequency peculiar to said fixed unit;

    resetting, when said portable unit having transmitted the registration signal receives the response signal, the counted value of the first predetermined reference time and starting next counting of the first reference time by said portable unit; and

    outputting, when said portable unit receives no response signal after having transmitted the registration signal for more than a predetermined second reference time longer than the predetermined first reference time, an indication of an unavailable situation on said portable unit.

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