Siemens AG 6ES5 421-8MA12 Digital Input Module

Siemens 6ES5 421-8MA12 is an eight-channel digital input module for SIMATIC S5 automation systems, delivering 24 V DC sensing across each input channel. Designed to integrate with Siemens ET 100U and ET 200U distributed I/O backplanes, it converts external sensor and switch signals into reliable digital inputs for the S5 PLC, enabling straightforward expansion of control logic without altering the existing wiring scheme. The module provides eight independent 24 V DC input lines, wired through a common L+ supply and M return terminal block, which streamlines field wiring and maintains consistent terminal layout across the S5 family. When mounted in a compatible S5 I/O rack, the 6ES5 421-8MA12 communicates with the PLC via the ET200U bus backplane, allowing real-time monitoring of sensors such as pushbuttons, limit switches, and proximity devices in manufacturing lines, packaging systems, and material-handling applications. This specific model offers a compact, scalable solution for adding discrete digital inputs to a Siemens S5 control system, helping to simplify expansion while preserving compatibility with existing I/O addressing conventions and wiring practices.