Patents Examined by Reinhard J. Esienzopf
  • Patent number: 5134708
    Abstract: Radio telephone apparatus for use in a cellular mobile telephone system includes an alarm to inform a user of a drop in signal strength of radio frequency signals received over an established communication link. Such a drop occurs, for example, when the user is approaching the boundary of a service area. Further, the mobile unit detect the presence or strength of a tone signal modulated on at least one of the received radio signals. The mobile unit disconnects the telephone link and returns to the standby mode if the tone signal is lost or becomes too weak.
    Type: Grant
    Filed: February 25, 1991
    Date of Patent: July 28, 1992
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Kuniyoshi Marui, Kiyoshi Hattori