1byone 100US-0002 Door Stopper Alarm Built-in Alert System, Works All Other Systems, 6.5 x 1.6 x 1.8 Motion Sensor Function: Equipped with an advanced pressure sensor technology. Simply place the alarm behind any door and, when opened, the pressure on the doorstopper will activate the +90db Alarm Compatible with all 1byone alarm receivers: The door stopper can be configured to send out signals to a distant receiver On/off switch to toggle activation: The on/off switch will prevent the alarm from accidental sounding Low-battery indicator light: Light indicator flashes if the battery is low. Without batteries it can also work as a wedge to prevent the door from opening or closing Battery powered: No wiring or complicated installation. Requires only 3x 1.5V AAA batteries (not included)