Patent ID: 7085569

Claim:
A cell search method for use in a mobile radio terminal adaptable to a predetermined number N of kinds of mobile telephone systems, where N is an integer not less than 1, the method comprising the steps of setting priorities for the mobile telephone systems, carrying out cell search for a high-priority mobile telephone system at first regular intervals when the mobile radio terminal is in a standby state in a low-priority mobile telephone system, immediately carrying out cell search for a high-priority mobile telephone system when a transmission-related operation is executed by the mobile radio terminal in case where location registration to a low-priority mobile telephone system has already been made, and, in a case where a cell of the high-priority mobile telephone system cannot be detected by the cell search for the high-priority mobile telephone system following the transmission-related operation, the cell search for the high-priority mobile telephone system is repeated at second regular intervals, and carrying out, upon detecting a cell of the high-priority mobile telephone system, location registration for the high-priority mobile telephone system to put the mobile radio terminal into a standby state in the high-priority mobile telephone system, each of the second regular intervals being of shorter time duration than each of the first regular intervals.