The Safety Beams Alarm Kit is a set of two devices that you line up to form an invisible infrared beam up to 60 feet long. When the beam is crossed, the alarm will sound. You can set it for either a loud alarm or a pleasant chime (as well as three volume settings). The device can be set for a single chime (great for businesses to announce when a customer enters the store) or to continue to go off until it’s manually turned off (ideal to alert you of a child or pet leaving a safe area, or a customer entering an unauthorized zone in a shop). The Safety Beams Alarm Kit costs $34.95 which is significantly cheaper than hardwiring a similar type alarm into your home or store.
Cop Security 15-946 Indoor/Outdoor Photoelectric Dual Beam Sensor Up to 550ft(indoor)/180ft(outdoor) (Black)