The Door Beacon - Door Knock Sensor<div style="text-align: left;"><strong>[Product Information]</strong><ul><li class="showHiddenFeatureBullets"><span class="a-list-item"> Knocking on the door shakes the sensor causing it to flash </span></li><li class="showHiddenFeatureBullets"><span class="a-list-item"> Adjustable sensitivity switch reduces false alerts/saves battery </span></li><li class="showHiddenFeatureBullets"><span class="a-list-item"> Three different mounting options included </span></li><li class="showHiddenFeatureBullets"><span class="a-list-item"> Includes one-year warranty and simple instructions </span></li><li class="showHiddenFeatureBullets"><span class="a-list-item"> Great for home， travel and noisy environments </span></li></ul></div><img src="http://ecx.images-amazon.com/images/I/41306oy2muL.jpg" noproxy>