PURPOSE: To perform carefully thought out fire monitoring corresponding to the environment of every case by automatically switching and setting the sensitivity of a sensor interlocking with the lighting control of illumination by the operation of a switching control switch or the control of air conditioning equipment.

CONSTITUTION: When the sensor S issues an accident warning by detecting a fire, an accident warning issuing signal is transmitted to a repeater 2 via a sensor line ls, and the repeater 2 receives the accident warning issuing signal, and transmits a multiplex signal on which an address is attached to an accident prevention receiver 1 side, then, alarm information is issued. Also, the driving signal of an accident prevention terminal is outputted in the multiplex signal from the accident prevention receiver 1 side via a multiplex signal line (l), and the repeater 2 receives the multiplex signal, and drives a required accident prevention terminal. Meanwhile, the illumination and air conditioning equipment are energized by operating the switching control switch SW provided in a room, and simultaneously, a switch control signal is outputted to a repeater 3 for sensitivity switching, and a sensitivity switching signal is outputted from the repeater 3 for sensitivity switching to the sensor S, then, the sensitivity of the sensor is switched and set. Thereby, it is possible to perform the carefully though out fire monitoring.