To realize a system that permits searching for or tracking a target at low cost by allowing the identification of the position of the target in areas scattered in a wide area such as a street, eases the protection of a bicycle or motorbike from theft or searching for such machine after stolen or prevents an aged man or a child from loitering about and allows searching for them by making a portable terminal added to the target in particular handy and inexpensive to an extent that it may be thrown away after use.

A target for searching for is made to carry a portable terminal 11 that can repeat intermittently the transmission of a signal string containing a predetermined natural identification signal by burst radio transmission, the signals are received by local control stations 21 to 24 arranged in various locations, the position of the portable terminal is identified or found from the positions of local control stations 12 or in addition the strength of reception. The portable terminals 11 are made cheap to an extent they may be thrown away after use for ensuring widespread use, and the use of solar cells, a swing type or other energy sources is proposed to eliminate the need for daily maintenance.