What button do I push on the instrument panel to activate DME in VOR navigation? For some strange reason I cannot seem to find any information about what button to push on the instrument panel to active the DME.  There is plenty of information about how DME works with interrogation and slant distance, but I cannot seem to locate any information about what button to actually push to activate DME when I am sitting in the cockpit (in a Cessna 172, for example) or where to look on the instrument panel to read the measured distance the DME is telling me.  So if the DME is measuring 8 nautical miles, where on the instrument panel will that &quot;8&quot; be displayed?
Typically, there isn't a &quot;button&quot; as such, you tune the DME to the frequency of the ground station (or slave it to the NAV radio).

The knob on the right is used to tune a frequency (shown before MHZ) when in &quot;frq&quot; mode, which is usually a VOR/DME. The numbers before NM is your distance to/from the station in Nautical Miles.