ITEM NAME:2-Channel Slotted Optical Switch Speed Detect Velocity Sensor Module I2N9 2-Channel Slotted Optical Switch Speed Detect Velocity Sensor Module I2N9 Product Name : Speed Detector Sensor Module;Chip : LM393 Channel Number : 2;Working Voltage : DC 3.3-12V PCB Board Size : 3.1 x 1.6cm/1.2" x 0.63"(L*W);Cable Length : 19cm/7.5" Materials : PCB;Main Color : Blue Application: Can be used to detect speed, count pulse, etc. Package Content : 1 x Speed Detector Sensor Module Note:Light shooting and different displays may cause the color of the item in the picture a little different from the real thing.The measurement allowed error is +/-1-3 cm..Application: Can be used to detect speed, count pulse, etc.