PHS is convenient mobile communication media in Japan. However, it is not available in house, since an output power of its terminal is approx. 10mW. In home use of PHS, home-antenna is used as a repeater to keep its communication condition. Its coverage is limited to near by the house, since its output power is less than 10mW. If a strolling aged with handy marker using PHS terminal exits from the house, he or she will exits from the coverage. PHS network watches each terminal. If the terminal exits from the coverage, the network detects it as a missing. If an alarm is transmitted by ordinary phone network as soon as from detection of missing, family of the aged can find the aged at near by the house. In this paper, the coverage of the home-antenna is measured. Two cases are measured by experiments. In the first case, PHS terminal is set to 2cm in height. In the second case, the terminal is set to 100cm in height. Former case simulates handy marker that is molded in a heel of shoes. Later case simulates the marker that is set to waist belt. In the result of the experiments, an ability of the detection system for strolling aged is indicated. The family can detect the aged by the alarm in the early stage of the strolling, since the coverage is less than 50m from the home in both case.