Introduction: Gray scale sensor is a electronic module to distinguish colors by detecting blackness. It outputs continous analogue signals, which is then changed by A/D connector into readings displayed via RCU. Users can distinguish colors by comparing the readings. It acts well in line-tracking game, with wide range of working voltage, when there is no serious environmental light interference. Working Theory Gray scale sensor emit light-wave to detected objects, and then measure object reflectivity by the reflected signal intensity. For deeper color object, such as black color, reflecting signal is weaker, and the output level is lower; for the lighter color object,such as white color, reflecting signal is stronger, thus output level is higher. The robot will be able to distinguish shade of color after comparing measure output level. The working power is widely as the circuit includes steady voltage, etc. and it can overcome the result of the circuit caused by power supply voltage fluctuations. http://www.roboexp.com/products/list.asp?id=83