Siemens SIMATIC PLC 6AG1321-7RD00-4AB0 SIPLUS S7-300 SM321 4DI NAMUR    FOR MEDIAL STRESS    WITH CONFORMAL COATING    BASED ON 6ES7321-7RD00-0AB0    .    DIGITAL INPUT OPTICALLY ISOLATE    4 DI, 24V DC, NAMUR/DIN 19234,    F. SIGNALS F HAZARDOUS AREAS,    CAPABLE OF DIAGNOST.,PTB-TESTED 6AG13217RD004AB0