Optical encoders use slits or markings on a disc that allow the transmitting LED to interrupt light shown through the disc. Optical discs are often made of glass or plastic. Glass discs are susceptible to breaking due to intense vibrations, and the plastic versions often have lower operating temperature ranges. Since optical encoders are simple devices, the pattern on the disc directly represents the output resolution of that encoder. The AMT rotor disc is made of a FR-4 PCB material making it suitable for use across a wide range of temperatures. The pattern used for disrupting the capacitive field is made of copper. Because of the digital nature of the AMT capacitive encoder and its use of a proprietary ASIC and processor, it is able to create a wide range of resolutions from the same rotor disc.