Explanation: Airborne Distance Measuring Equipment (DME) systems are designed for convenience and integration with primary navigation aids. When a pilot selects a specific VHF frequency for a **VOR (VHF Omni-directional Range)** or an **LOC (Localizer)**, the aircraft's DME interrogator automatically tunes its UHF transmitter and receiver to a corresponding paired frequency. This pairing ensures that the DME provides slant range distance to the same navigation facility (or a co-located DME transponder) that the pilot is tracking for bearing (VOR) or lateral guidance (LOC). Marker beacons provide distinct position indications and are not used for DME pairing. Glideslope frequencies are paired with LOC frequencies, but the DME's *primary tuning trigger* comes from the selected VOR or LOC frequency, not the glideslope itself.