PURPOSE: To extend the service life of the battery of a slave station, by including the transmission timing information of an answer back signal from each slave station in a group designation signal, forming a bundle of the signals of plural groups sequentially, and transmitting it from a master station intermittently.
CONSTITUTION: A transmission signal from the master station is divided into plural groups, and each group is constituted of the group designation signal set differently at every group and a signal having information common to each group, and the transmission timing information of the answer back signal from each slave station is included in the group designation signal, and the signals of the plural groups are transmitted intermittently from the master station as a sequence of bundle. Meanwhile, each slave station receives the transmission signal intermittently, and each slave station, when judging that its own station being called, transmits the answer back signal immediately after completing transmission to the master station based on the transmission timing information. In such a way, it is possible to extend the service life of the battery of the slave station.
YAMAJI SATORU
SEKI YOSHINORI
TADA JUNJI
