Introduced during World War II to protect military aircraft from being fired upon accidentally by “friendly” troops when returning from missions, today’s IFF Systems have evolved and expanded on the core radar-based “interrogation and response” signal transponder systems and are now used by military and civilian air traffic controllers. In national defense, Identification Friend or Foe is seen as a Combat Identification (CID) system within C4ISR structures and not only supports mission safety worldwide, but also enhances flight tracking data collection.

Over the decades following their introduction, the electronic IFF technologies mounted or carried on the ground, in aircraft, and on related platforms – the physical devices – have evolved significantly. Newer IFF technologies are built on digital architectures, many reduced in size and weight to support SWaP goals, and user interfaces simplified. Core IFF technologies currently in use include the following:

  • Identification Friend or Foe (IFF) Interrogators are electronic devices that emit an “interrogating” radio signal at one frequency, prompting an IFF Transponder to emit a reply signal at a different frequency, indicating that an approaching aircraft is “friendly.”
  • Identification Friend or Foe (IFF) Transponders are transmitter/responders mounted in aircraft, naval vessels, and some ground vehicles to identify the craft as “friendly” by responding to “interrogation” signals emitted by IFF system Interrogators.
  • Identification Friend or Foe (IFF) Combined Interrogator Transponders (CITs) consolidate the functions of dedicated IFF Interrogators and Transponders into a single unit, specifically for use with modern mobile platforms to identify “friendlies” and save lives within secure zones.
  • Identification Friend or Foe (IFF) Cryptographic Computers encrypt signals being sent by IFF Interrogators and encodes replies from corresponding Transponders. This makes it difficult for adversaries to steal identification codes to imitate friendly aircraft for executing surprise attacks.
  • Identification Friend or Foe (IFF) Emulators provide testing of IFF Interrogators and Transponders, including cryptographic capabilities, in multiple Modes appropriate to each system.
  • Identification Friend or Foe (IFF) Antennas enhance both Interrogator and Transponder signals, work with all standard IFF Modes, and are often integrated to also support other C4ISR systems, like Secondary Surveillance Radar (SSR) and air traffic control (ATC) radar signals.

As with the electronic IFF devices, the signals, codes, frequencies, and communication Modes underlying the IFF system have also evolved. These advances have been to improve performance system wide, as well as to block decryption and exploitation by adversaries. The current IFF system is Mark XIIA, and the Mode 5 waveform is its most recent implementation.

While all IFF system technologies must adhere to core USDoD and NATO Identification Friend or Foe specifications and standards, defense industry manufacturers with an extensive IFF history and broad IFF perspective also build future growth capabilities into their devices. That, combined with ample training and support services, assures both government and private sector buyers of dependability, value, and potential for innovative advancement.


This information page is provided as a service to our readers by BAE Systems, Inc., a U.S.-based world leader in aerospace, defense, power, and intelligence solutions. Learn more about us here.

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