- Electromagnetic sensor technology- Simply hang on door or window (metal) handles、 when someone touchs the handle on the other side、 the alarm siren goes off- Prevent and scare theives away before even they get in- 120dB ultra load siren- Powered by?1 x 9V battery                                                                                                                                Dimensions: 3.94 in x 2.17 in x 0.98 in<br />Weight: 2.75 oz