Siemens 6ES5420-4UA11 is a SIMATIC S5-420 digital input module that provides 32 digital inputs at 24 V DC in a compact non-floating (Compact Version U) format, designed for use with S5-420 controllers such as the S5-135U/155U/H series. It accepts standard 24 V DC logic signals from sensors and switches to feed the PLC input bus, serving as a straightforward I/O expansion for discrete sensing in manufacturing and process equipment. The module is also catalogued as 6ES54204UA11 and is commonly used to interface multiple digital devices to legacy Siemens S5 systems.
