In a previous article, said:
How does the system know which are the outer dme "targets"? Is it
just the weaker dme transmissions that are received by the ground
station that are dropped? Stan

By response time. It sends out a signal, and the first N to respond are
tracked.

--
Paul Tomblin http://blog.xcski.com/
"Whoah, whoah! A fat sarcastic Star Trek fan? You must be a devil with the
ladies!" - Simpsons