Patent ID: 8269642

Claim:
An alarm system, comprising: a master alarm device; and at least one slave alarm device, the master alarm device and the at least one slave alarm device all having an identical configuration and performing transmission and reception therebetween, wherein: the master alarm device and the at least one slave alarm device store group information containing at least a master alarm device address and a slave alarm device address, and store a master unit switching order which is information predetermining the order of switching the master unit for all alarm devices, the master alarm device determines which slave alarm device is to next operate as the master alarm device based on the master unit switching order, and transmits a switching request signal to all slave alarm devices at a predetermined timing, the switching request signal containing at least an own address and an address of the slave alarm device that is to operate as the master alarm device next; upon reception of the switching request signal, the slave alarm device that is to operate as the master alarm device next judges whether or not switching is possible based on switching availability judgment information for judging whether or not the switching is possible between the slave alarm device and the master alarm device, and transmits, as a response, a result of the judgment to the master alarm device and all the other slave alarm devices, and when it is judged that the switching is possible, starts operating as the master alarm device; and the master alarm device and all the other slave alarm devices update the group information when they have received a response to the result of the judgment from the slave alarm device.