What does it mean to "lock on" to a DME ground station? I was just reading about the working of the DME the other day and then I read a para which said:


  The aircraft interrogator "locks on" to the DME ground station once it
  recognizes a particular pulse sequence having the same spacing as the
  original interrogation sequence


Can anybody please elaborate on the above statement? I just want to know what is "lock on" and how does an aircraft interrogator lock on to a DME ground station?
"Lock-on" just refers to a unit receiving multiple different response signals in response to its interrogation broadcasts, scanning for the signal it's looking for, and when it finds the signal who's encoding matches its channel selection, it starts to process that signal and ignores all others.  It's locked on to that signal.