PURPOSE: To flicker red display lamps displaying the operated state of plural pumps which are respectively provided for plural monitoring ranges in a tunnel in synchronizing with plural red display lamps in the other monitoring ranges at the time of operating the pumps.

CONSTITUTION: In an abnormal case when the pumps corresponding to the plural monitoring ranges in the tunnel are driven, a disaster prevention board 2 issues a display lamp flickering command to respective repeater boards 3 in the monitoring ranges and the starting control circuits 13 of the respective repeater boards 3 receiving the command output a flickering starting control signal to a red display lamp control circuit 17. At this time, each red display lamp control circuit 17 receives a synchronizing pulse signal constantly outputted from the disaster prevention board 2 from respectively common red display lamp synchronizing signal line 10 and prepares a flickering driving signal based on the synchronizing pulse signal so that the deviation of flickering timings is not generated between the red display lamps 5 in the plural monitoring ranges.