PURPOSE: To improve the reliance on transmission and reception of communication signal wireway and to enable each function to automatically diagnose by itself by adopting a multiple signal communication system using a serial transmission for the transmission and reception of communication signal between an operating box and a control board, between the control board and operation indicating board, etc.

CONSTITUTION: Each of control printed boards 1-1 to 1-n is provided in a control board 1 correspondently to each of fireproof zones and connected to each of operating boxes 2-1-1 to 2-n-n, respectively. A serial transmission wireway 3-1 between each control board 1 and each operating box 2 is connected in multidrop system of R485(4). Control printed boards 1-1 to 1-n are also connected to one another through RS485, and a common signal is communicated as a control pass on the serial transmission wireway between the control printed boards 1-1 to 1-n. A RS485/RS232C converter 6 is disposed on the serial transmission wireway and connected to an LCD indicator 7. The transmission and reception are carried out between the control board 1 and the operating box 2, and operation indicating board 8 once a month to check the operation thereof.