The AMT series modular encoder consists of three basic parts as shown in the illustration here. The AC field transmitter emits a signal that is modulated by the metal pattern on the rotor as it turns. The sinusoidal metal pattern on the rotor creates a signal modulation that is repetitive and predictable. This occurs as a result of varying capacitive reactance between the signal generated by the transmitter and the metal on the rotor. The field receiver uses a proprietary ASIC to convert the modulated signal into output pulses that can be read by the same circuits used to receive optical encoder output. If the reader has ever used digital calipers, they are already familiar with capacitive encoding. The code generation used in digital calipers for decades is the same technology built into the AMT series encoders.