SimpliSafe MS1 Extra Motion Sensor ( Original System) Full Room Coverage - Detects motion within 30 feet. The sensor has a field of vision of 90 degrees, giving you a full range of coverage when placed in a corner. Flexible Install - The sensor is shaped to stand on a shelf, adhere to a wall, or fit in a corner for maximum room coverage. Set the sensor to be active only in away mode (so that you wont trigger it when youre at home) or both home and away modes (for rooms that you want covered with a motion sensor while youre home). Pet Friendly - Your dogs and cats under 50 lbs wont trigger the alarm. Weve designed the sensor to be less sensitive to motion close to the ground. Works only with the Simpli Safe Original System