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Radio telephone apparatus having a service area confirmation

  • US 5,444,765 A
  • Filed: 04/18/1994
  • Issued: 08/22/1995
  • Est. Priority Date: 03/23/1992
  • Status: Expired due to Term
First Claim
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1. A cellular radio telephone for use in a plurality of cellular radio systems, each having one or more base stations that broadcast radio signals throughout a service area over a paging channel and over an access channel, the radio signals including system identification data identifying the cellular radio system from which the radio signals are broadcast, said cellular radio telephone comprising:

  • storing means for storing system identification data of one of said cellular radio systems to establish said one cellular radio system as a home cellular radio system and to establish a service area throughout which said home cellular radio system broadcasts as a home service area;

    establishing means for establishing a paging channel with a cellular radio system in whose service area said cellular radio telephone is then present in response to power-up of said cellular radio telephone and for establishing an access channel with a cellular radio system in whose service area said cellular radio telephone is then present in response to an input of call placement request by a user;

    detecting means coupled to said establishing means for detecting system identification data from the radio signals broadcast over said established paging channel by said cellular radio telephone system in whose service area said cellular radio telephone is present at power-up of said cellular radio telephone and for detecting system identification data from the radio signals broadcast over said established access channel by said cellular radio telephone system in whose service area said cellular radio telephone is present at the input of the call placement request;

    comparing means, coupled to said detecting means and said storing means, for comparing the system identification data detected from the radio signals broadcast over said established paging channel with the stored system identification data and for comparing the system identification data detected from the radio signals broadcast over said established access channel with the stored system identification data; and

    indication means, coupled to the comparing means, for providing an indication of roamer status if the system identification data detected from the radio signals broadcast over said established paging channel does not coincide with the stored system identification data and for providing an indication of roamer status if the system identification detected from the radio signals broadcast over said established access channel does not coincide with the stored system identification data.

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