Editing Tactical air navigation system (section)

===Operating modes===
There are two basic channel configurations available: X (the original implementation) and Y (added in the 1960s to expand available channels and reduce mutual interference between closely-spaced stations). These configurations differ in pulse-pair width, fixed receiver response delay, and polarity of frequency offset from the interrogation channel. TACAN interrogators can operate in four modes: receive (for bearing/identification only), transmit/receive (for bearing, range, and ID), and air-to-air versions of the previous two.

The typical TACAN onboard user panel has control switches for setting the channel (corresponding to the desired station's assigned frequency), the operation mode for either transmit/receive (T/R, to get both bearing and range) or receive only (REC, to get bearing but not range). Capability was later upgraded to include an air-to-air mode (A/A), where two airborne users can get relative slant-range information depending on specific installations,<ref>{{cite web | url=http://www.patentstorm.us/patents/5128873/description.html | author=Rockwell International | date=July 7, 1992 | title=Aircraft rendezvous using low data rate two-way TACAN information | url-status=dead | archive-url=https://web.archive.org/web/20110612222405/http://www.patentstorm.us/patents/5128873/description.html | archive-date=June 12, 2011 }}</ref> though an air-to-air mode allows distance to be established between transmitters/receivers.

{| class="wikitable"
|+ TACAN operating specifications, derived from MIL-STD-291C<ref>{{Cite web |title=MIL-STD-291 C TACTICAL AIR NAVIGATION SIGNAL |url=http://everyspec.com/MIL-STD/MIL-STD-0100-0299/MIL-STD-291C_11561/ |access-date=2024-03-18 |website=everyspec.com}}</ref>
! Channel/operating mode !! Interrogator frequency (MHz)/channel !! Response frequency offset (±63 MHz) !! Interrogator pulse-pair width (μs) !! Response delay spacing (μs) !! Response pulse-pair width (μs) !! Main/auxiliary reference burst length (pulse pairs) !! Main/auxiliary reference burst pulse-pair spacing (μs) !! Main/auxiliary reference burst synchronization point
|-
!X channels, air-to-ground
| rowspan=4 | 1025-1150 (1-126) || negative (1-63)<br>positive (64-127)<br /> || 12 || 50 || 12 || 12/6 || 12/24 || rowspan=2 | Positive peak of AM signal pointed due east when main burst triggered; auxiliary burst synchronized to same event, but suppressed during main burst transmission
|-
!Y channels, air-to-ground
| rowspan=3 | positive (1-63)<br>negative (64-127)<br /> || 36 || 74 || 30 || 13/13 || 30/15 <br>(both single pulse)<br />
|-
!X channels, air-to-air
| 12 || 62 || rowspan=2 | single pulse || rowspan=2 colspan=3 | Same as air-to-ground, if supported 
|-
!Y channels, air-to-air
| 24 || 74
|}