SIMATIC S7/PCS7, SM 321 DIGITAL INPUT MODULE, 16 DI, 24V DC, 1 X 40 PIN, CAPABLE OF DIAGNOSTICS, FOR CONTACTS (CONNECTED/ UNCONNECTED), NAMUR SENSOR, 3/4-WIRE-BERO, WITH FLUTTER MONITORING, PULSE LENGTHENING, WIRE BREAK DETECTION, IM153-2 INTERFACE MOD. REQUIRED