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Out-of-range warning system for cordless telephone

  • US 5,373,548 A
  • Filed: 04/08/1994
  • Issued: 12/13/1994
  • Est. Priority Date: 01/04/1991
  • Status: Expired due to Fees
First Claim
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1. A cordless telephone unit having a handset unit and a base unit, the base unit being connectable to a telephone network and having actuatable means for seizing and releasing a telephone line of said telephone network, the handset unit having means for providing dialing and data signals to said telephone network, comprising:

  • duplex RF communications means between the handset and the base unit, said communications means including a base transmitter means and a base receiver means disposed in the base unit and a handset transmitter means and a handset receiver means disposed in the handset, said duplex RF communications including a carrier signal which is FM modulated with a first percentage of deviation,signal strength determination means disposed in the base unit for determining the strength of the signal received by the base receiver means from the handset transmitter means,range determination means disposed in the base unit for determining from the signal strength determination means whether the handset is at an out-of-range distance from the base unit,warning means disposed in the base unit for transmitting a plurality of warning signals from the base unit to the handset when it is determined by the range determination means that the handset is at an out-of-range distance from the base unit, said warning signals FM modulating the carrier signal at a second percentage of deviation which is greater than the first percentage of deviation in order to provide, a warning signal at the handset at an out-of-range distance, andmeans disposed in the base unit for putting the cordless telephone unit in an "on" hook status after a predetermined number of warning signals are transmitted.

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