The DeltaV I/O subsystem supports multiple types of I/O cards, including analog and discrete input and output cards, HART output and input cards, serial cards, the H1 Fieldbus card, AS-Interface card, Profibus DP card, RTD, ohms, Thermocouple, mV, Multifunction, and the SOE (Sequence of Events) card. The I/O subsystem consists of a terminal block that snaps onto the carrier to provide screw termination for field wiring and the actual I/O card that snaps over the terminal block and onto the carrier. The I/O card converts field signals to the appropriate format for control and communications.