With the safety beam, you know when someone "crosses the line". This high tech device creates an invisible infrared beam up to 60 feet long and sounds a loud alarm, pleasant chime, or multiple chimes when the beam is crossed. Retail stores and businesses can use the one chime feature to announce customers entering the store. The chimes setting can be used to bring attention to someone entering an "off limits" area (in this mode the chime sounds for 30 seconds and then resets). The alarm's decibel rating is 110. Not only can it be used as an invisible playpen to alert you when your child or pet leaves a safe area, it can also be used at night to scare off intruders. Please note that this item works best when it is placed one foot off the ground or higher. The distance indicator has a maximum distance of 60 feet and can be set to high or low. The dimensions are 4 and three-eighths inches x 3 inches x 1 and one-eighths inches. The volume of the chime can be set to low, medium, or high. Covered under a 90 day warranty. Three AA batteries (not included) can be used in place of the two 6 volt AC adapters if you prefer to go cordless.