Plain English Meaning

Short radio signals the aircraft sends out to a ground station to ask, in effect, 'how far away are you?' The station answers, and the equipment uses the time it took to work out the distance.

Full Definition

Paired radio frequency pulses transmitted by an aircraft's DME (Distance Measuring Equipment) unit to a ground station, asking the station to respond. The ground station receives these pulses, waits a fixed delay, then transmits reply pulses on a different frequency. The aircraft's DME measures the round-trip time between sending the interrogating pulses and receiving the replies, then converts that time into a slant-range distance to the station.

Context Anchor

Seen in DME system descriptions, especially when explaining how airborne DME equipment communicates with a ground station to produce a distance readout.