PURPOSE: To prevent an alarm signal from being automatically transmitted to the crime preventing, receiver side at the time when the crime preventing receiver side is set to the precaution state but a window or a door is opened from indoors.

CONSTITUTION: Repeaters 1 and 1' for crime prevention switch are provided with crime prevention switch terminals T1 and T2 to which crime prevention switches 100 and 100' are connected, crime preventing receiver terminals T3 and T4 to which a crime preventing receiver is connected, precaution control contacts SW1 and SW3 which stop or allow the transmission of alarm signals inputted from crime prevention switch terminals T1 and T2 to crime preventing receiver terminals T3 and T4, and a human body detecting sensor 10a, and a precaution control part 10 is provided which switches precaution control contacts SW1 and SW3 to the break side to stop the transmission of alarm signals to crime preventing receiver terminals T3 and T4 in the period when a human body is detected by the sensor 10a.