Fort Smart Vibration Sensor for Smart Home Alarm System. The sensor detects vibrations from 300Hz to 3KHz when placed on a flat surface and transmits a radio frequency signal to the Smart Alarm Hub (sold separately) to sound the alarm when intruders come knocking (or banging). It is easy to install using the provided mounting screws and wall plugs, simply remove the battery strip, pair the device and you are good to go.