Standing at 12cm tall, the Official Doctor Who Dalek Line Tracker.
The technology behind this line tracker belongs to 2 sensors located on the bottom of the Dalek. Each sensor has a pair of infrared LEDs and an infrared light sensor that controls the corresponding motor.
The infrared LED generates the signal to the paper and the receiver will obtain the reflected signal to differentiate the line from the surrounding area. Once the unit detects the line it will drive the wheels to run. So the reflection of the light is key to drive the wheels.
Requires AAA batteries, not included.