The encoder is a device or a transducer or a circuit.The encoder will convert the information from one format to another format i.e like electrical signals to counters or a PLC. The feedback signal of the encoder will determine the position, count, speed, and direction. The control devices are used to send the command to a particular function.

Fig: Encoder

The decoder is a circuit used to change the code into a set of signals. The name its self tells the decoder because it has the reverse of encoding. The decoders are very simple to design.

Fig: Decoder