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ABB MM21 is a legacy Hartmann & Braun Contronic plug-in module used within an established process-control hardware configuration.
Replacement suitability depends on the complete MM21 label, hardware revision, rack position, rear-connector keying, board population, and original cabinet drawings.
Before removing the installed module, record its configuration, indicator states, adjacent-module references, connector orientation, and every affected signal assignment.
ABB MM21 H&B Contronic Plug-in Module Manuals, Product Family, Links
Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
Before replacement, compare the complete module marking, board population, connector keying, and rack slot. Record all wiring references, jumper or selector settings, and diagnostic indications before removing the module.





