Which two navigation aids form the paired channel that DME systems auto-tune to?

• A. VOR and marker beacon.
• B. VOR and LOC.
• C. Marker beacon and glideslope.
• D. LOC and glideslope.

Answer: (B)

DME is designed to work with VOR or ILS components. The DME transmitter is paired with either the VOR or the localizer of an ILS, and the DME channel you use is automatically selected to match that VOR or LOC signal. When you tune a VOR frequency, the DME auto-tunes to the corresponding DME channel so you can read distance to that VOR/DME facility. The same happens if you tune the localizer frequency—DME pairs with that LOC signal. Marker beacons and glideslope are separate ILS elements and do not provide DME data, so they don’t form the paired DME channel. So the two navigation aids that establish the paired DME channel are the VOR and the localizer.