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A DME (and VOR) may only maintain a single collocation relationship at a time, which means that it is not possible to collocate a VOR with two different DMEs, and vice versa. The same is valid for a DME and NDB collocation.
A particular DME may also be defined as a part (NavaidEquipment) of an Navaid of type 'ILS' or 'MLS'. A single DME can be part of more than one ILS/MLS but each ILS can have just one assigned DME.
For more details see topic Landing Systems & Navaid Collocation.
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