Siemens 6ES5440-8MA21 Analog Input Output Module

Siemens 6ES5440-8MA21 is a SIMATIC S5 digital output module (DO 440) that provides four 24 V DC outputs at up to 2 A per channel. The module uses non-floating outputs and is designed for backplane mounting in S5 systems, compatible with S5-90U, S5-95U, and S5-100U controllers, as well as ET 100U and ET 200U backplanes. It is used to switch 24 V DC loads such as relays, contactors, indicators, and other actuators in legacy Siemens automation installations. The 6ES5440-8MA21 is widely referenced by distributors and repair catalogs as the four-channel DO 440 module, matching the 24 VDC, 2 A per channel rating and the non-floating configuration. When installed, ensure each output remains within the 2 A limit and observe proper wiring to the backplane to maintain reliable operation in industrial environments.