An alarm device comprising: a reception circuit section which receives event signals containing a transmission source code from other alarm devices; a transmission circuit section which transmits event signals containing a transmission source code to the other alarm devices; a sensor section which detects abnormal conditions; an alert section which outputs an alarm; an alarm registration section which, when a registration send mode is in effect to form a linked group, sends a registration event signal containing the transmission source code, and when set to a registration receive mode, registers the transmission source codes contained in the event signals received from the other alarm devices in a memory; an abnormal condition monitoring section which, upon receiving an abnormality detection signal from the sensor section, outputs an abnormality warning of a linkage-source to the alert section while also transmitting the event signal indicating the abnormal condition to the other alarm devices, and upon receiving the event signal indicating an abnormal condition from the other alarm device, if the transmission source code included in this event signal matches with a pre-registered transmission source code registered in the memory, outputs an abnormality warning of a linkage-destination to the alert section; a registration mode switching section which switches the registration send mode and the registration receive mode; and a transmission power switch control section which, when the registration send mode is initiated by the registration mode switching section, reduces the transmission power of the transmission circuit section beyond that of normal operation. a reception circuit section which receives event signals containing a transmission source code from other alarm devices; a transmission circuit section which transmits event signals containing a transmission source code to the other alarm devices; a sensor section which detects abnormal conditions; an alert section which outputs an alarm; an alarm registration section which, when a registration send mode is in effect to form a linked group, sends a registration event signal containing the transmission source code, and when set to a registration receive mode, registers the transmission source codes contained in the event signals received from the other alarm devices in a memory; an abnormal condition monitoring section which, upon receiving an abnormality detection signal from the sensor section, outputs an abnormality warning of a linkage-source to the alert section while also transmitting the event signal indicating the abnormal condition to the other alarm devices, and upon receiving the event signal indicating an abnormal condition from the other alarm device, if the transmission source code included in this event signal matches with a pre-registered transmission source code registered in the memory, outputs an abnormality warning of a linkage-destination to the alert section; a registration mode switching section which switches the registration send mode and the registration receive mode; and a transmission power switch control section which, when the registration send mode is initiated by the registration mode switching section, reduces the transmission power of the transmission circuit section beyond that of normal operation.