If tethered will require one of these a 8138001 Bus Adapter to expand the MTSIII Dimax port
8138001 Bus Adapter – Massoth Elektronik GmbH
Very briefly, if wireless and using 433MHz , in most cases the Navigators are usually in the default factory state, check RC frequency is the same, likely the device IDs will be identical, if so change the visiting Navigator to another ID, if in doubt consult the following sections of the Navigator manual.
Section 8.4 Device ID (Identification number)
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Section 8.9 RC mode configuration.
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