PURPOSE: To prevent response signals to a reception part from increasing and prevent the process of a reception part from being delayed by making a multiple signal type fire sensor, which has received a level stop instruction, not respond at its fire decision level.

CONSTITUTION: A receiver decides the level of a signal received from the multiple signal type fire sensor, and sends out a level stop instruction stopping the multiple signal type fire sensor from sending out an answer signal thereafter as to the received level signal unless the fire corresponding level of the received level signal corresponds to a desired fire corresponding level, and the multiple signal type fire sensor which has received the level stop instruction does not respond to the receiver by system polling or point polling. Therefore, even when the multiple signal type fire sensor is turned ON and OFF repeatedly with smoke density lower than the level at which the receiver decides a fire, no unnecessary response signal due to it is sent to the receiver, so the process of the receiver is prevented from being delayed.