What it is and where it fits
The Siemens 6ES7131-4FB00-0AB0 is a SIMATIC DP electronic module for ET 200S, packing 2 digital inputs rated for 230 V AC (47 to 63 Hz) into a 15 mm wide slice. It's the go-to for sensing AC line signals in a distributed I/O rack — think panel-level monitoring of motor starters, valve position feedback, or any 230 VAC dry contact. The module ships as a 5-unit bundle, so one order code covers a full rack segment.
Isolation and wiring reality
Galvanic isolation tested at 4 000 V DC between channels and backplane bus. No isolation between the two input channels. Maximum shielded cable length 1 000 m, unshielded 600 m. Input draws 5 mA typical at signal "1", range 5 to 15 mA.