I/O modules provide the signal interface between industrial controllers and field devices such as sensors, transmitters, switches, relays, valves, and actuators. Their architecture typically combines channel electronics, signal conditioning, isolation, conversion circuits, bus interfaces, status indication, and terminal connections. The category includes analog input and output, digital input and output, mixed I/O, remote I/O, and specialized interface modules. Technical characteristics vary by module and include channel count, signal range, voltage or current type, isolation level, resolution, update time, diagnostic capability, and supported backplane or fieldbus. Functionally, I/O hardware acquires process signals, converts them into controller data, and transfers output commands to field equipment. Selection should match the controller family, signal specification, wiring architecture, channel density, and exact module revision.
