SERIAL INTERFACE UNIT (SIU). THIS IS AN ELECTRICAL COMPONENT THAT FORMS PART OF AN ELECTRICAL CONTROL SYSTEM. THE FUNCTION OF THE SIU IS TO INTERFACE BETWEEN THE CONTROL PANEL (PLC) AND EXTERNAL DEVICES, SUCH AS VALVES, PNEUMATIC DEVICES, SENSORS, CARRYING OUT INSTRUCTIONS SUCH AS SWITCHING ON/OFF. THE SIU'S CONTAIN COMPONENTS SUCH AS MICROPROCESSORS, MEMORIES, POWER REGULATORS, OSCILLATORS, ACTUATORS, COMMON PASSIVE COMPONENTS MOUNTED ON PRINTED CIRCUIT BOARDS. THE CONTROL PANEL CANNOT OPERATE WITHOUT THE SIU.

GIR 1&6 COMMISSION IMPLEMENTING REGULATION (EU) NO 1247/2011 NOTE 2 (b) TO SECTION XVI