Editing Tactical air navigation system (section)

===Ranging===
Range information is functionally identical to the method provided by civilian DME: pairs of 3.5 microsecond (μs) pulses (measured edge-to-edge at 50% modulation strength) from an aircraft are repeated by the station being interrogated, using the round-trip time to calculate slant-range distance. Randomized spacing between interrogation pulse-pairs allows the interrogator to separate its own signal from that of other aircraft, enabling multiple users to access the ranging function without mutual interference. A fixed-round trip delay time (dependent on system mode) is added to each pulse-pair when being retransmitted by its station. The interrogator will generate up to 150 pulse-pairs per second when first acquiring a station in range in "search" mode, then drop down to ≈30 per second when acquired in "track" mode. Memory circuits in the ranging function enable a track to be quickly reestablished when ranging pulses are temporarily suppressed by other TACAN functions (see below).