The Optek OP644SL Phototransistor is a top-view pillar-style optical sensor designed for use in a variety of applications. It features a 890nm peak wavelength, a wide viewing angle of up to 120°, and a fast response time of less than 1ms. The OP644SL is ideal for use in applications such as motion detection, presence detection, and object detection. It is also suitable for use in industrial automation, robotics, and medical equipment. The OP644SL is designed to be robust and reliable, with a long life expectancy and low power consumption. It is also easy to install and configure, making it a great choice for a wide range of applications.