AS-Interface (Actuator Sensor Interface, ASi) is an industrial networking solution (physical layer, data access method and protocol) used in PLC, DCS and PC-based automation systems. It is designed for connecting simple field I/O devices (e.g. binary ON/OFF devices such as actuators, sensors, rotary encoders, analog inputs and outputs, push buttons, and valve position sensors) in discrete manufacturing and process applications using a single two-conductor cable.
AS-Interface is an 'open' technology supported by a multitude of automation equipment vendors. The AS-Interface has been an international standard according to IEC 62026-2 since 1999.