Photoelectric safety sensors are designed for anti-pinching risk among automatic sliding door system. Working with other safety control parts, such as safety thru-beam sensors and safety light grids. these sensors make sure that a intime pause occurs when an unauthorized access or an entry into safety zone is detected. This model (#TK-218D ) infrared photo beam sensors have a valid detection range of 10 metre distance, which is enough for most sliding door in many a scenario. They are very easy to install and wire, quite a necessary and safe part for the auto sliding door.