M-series FOUNDATION™ fieldbus I/O is a modular subsystem that communicates digitally with field devices, increases your input/output capacity, and gives you access to more information about your process than conventional I/O subsystems. It is equipped with function and field-wiring protection keys to ensure that the correct I/O card is always plugged into the corresponding terminal block. M-series FOUNDATION fieldbus I/O greatly enhances device diagnostics that affect your control strategy and alerts operators to device malfunctions.