PGS-047 earthquake alarm has two sensors, the sensor in the left side if for detecting the P wave and the other sensor in right side is for detecting the S wave, so, the item can detect the P wave except the shallow earthquake, maybe it can't be detected sometimes. After the P wave, the S wave also can be detected, it will make different sounds when detected the P wave and S wave. S wave (red light( is the destructive earthquake wave and the alarm will detect first the compression waves (P waves --red light) with a particular sound. The time between both alarms are apron 10-15 seconds. When the S wave is coming to your area then the alarm will change its sounds. So, there is two types of sounds for each distinct wave. The yellow LED will be flashing when the batteries energy is low (2 AAA included). 3 easy steps to install it: 1. You can stick it to the wall or hang it (adhesive paper, screw and screw anchor are included). 2. Keep the top bubble in the center of the circle. 3. Turn the switch on.

Product Features and Technical Details