If you update your RM4200D to the Series 52 firmware generation, it is necessary to exchange the Communication Controller. Instead of the RM420-850, you need an RM420-852/853 controller module. If your console contains a TFT display, you need to rewire it after the controller exchange.
The following diagram shows the conventional wiring of the TFT screen of an RM4200D console equipped with an RM420-850 Communication Controller.
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After the update to the Series 52 firmware generation, the TFT display must be connected to the Communication Controller module in the following way.
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Please find detailed information on the wiring of the RM420-852 and RM420-853 controller modules in the 52/MX Manual and in the 52/MX Installation Guide.