I/O modules connect sensors and actuators are the interfaces of the system to the process.
Digital I/O modules acquire the binary control signals to and from the process level.
Analogue signal modules acquire the analogue control signals (e.g. measurement data) to and out of the process level. Depending on the application and type the control signals are acquired from the process level and converted into interpretable signals for controlling. Analogue output modules convert the internal control signals into signals suitable for the process level.
