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Cordless telephone apparatus which restores radio channels after power loss

  • US 5,426,690 A
  • Filed: 07/30/1993
  • Issued: 06/20/1995
  • Est. Priority Date: 08/04/1992
  • Status: Expired due to Fees
First Claim
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1. A cordless telephone apparatus comprising:

  • a base unit connected by wire to a public telephone line circuit;

    a remote unit driven by an internal replaceable battery power source;

    a radio transmit-receive circuit, provided in the remote unit, and controlled by a main control circuit, that can transmit modulated call information from the remote unit via one of a pair of radio channels with mutually different frequencies for two-way radio communication, and can demodulate call information received from the base unit via the other channel;

    a radio transmit-receive circuit, provided in the base unit, and controlled by a main control circuit, that can demodulate call information received from the remote unit via said one of a pair of radio channels, and can transmit from the base unit modulated call information carried by said other channel;

    control circuit, provided in the base unit, that detects received field strength on said one of a pair of radio channels, output an out-of-range signal on said other channel via the transmit-receive circuit provided on the base unit if the detected field strength is below a prescribed field strength, and breaks the connection with the public telephone line circuit if the received field strength remains below the prescribed field strength for a prescribed time period;

    a channel connection state volatile memory area, provided in the remote unit, in which channel establishment data is stored when two-way radio communication was established via the pair of radio channels between the base unit and the remote unit, and in which channel non-establishment data is stored when said communication was not established;

    a backup power source, provided in the remote unit, that maintains the channel establishment data or channel non-establishment data selectively stored in the volatile memory area even if the supply of power from the battery source is interrupted; and

    a call resumption control circuit, provided in the remote unit, that resumes transmission of call information from the remote unit, when it determines that the result of a check of the volatile memory area when power was supplied from the battery source in the remote unit is that channel establishment data is stored in said volatile memory area and when an out-of-range signal is detected via the transmit-receive circuit in the remote unit.

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