Identification friend or foe
From Freepedia
In telecommunications, identification, friend or foe (IFF) is an identification system designed for use during hostile conditions, that enables military aircraft, or both civilian and military air-traffic controllers to distinguish friendly aircraft, vehicles, or forces from the enemy, and also to track them.
The IFF system traditionally used coded radar signals (also known as interrogations) to automatically trigger the aircraft's transponder in an aircraft "painted" by the radar. A transponder responds,
- in a military aircraft (other military vehicles or units similarly equipped) equiped with an IFF capable transponder, by returning a correctly coded reply signal only when the incoming interrogation is identified as part of the friendly forces network;
- if no IFF response is generated a civil interrogation is generated and the aircraft, by returning a proper code can then be identified.
In an IFF network both the interrogation and reply are verified as friendly. Interrogation validation prevents an interrogator from using a transponder's replies for tracking purposes.
Major benefits of IFF include:
- Avoiding "friendly-fire" or fratricidal attacks
- Reducing attacks on civilian aircraft
- Improving, by coordination among friendly forces, decisions about tactics.
- Providing automatic information to ground stations via the return signal.
The secondary surveillance radar (SSR) system used in modern air traffic control systems is an outgrowth of the military IFF system used during World War II. The IFF equipment carried by modern military aircraft is compatible with the SSR transponder system used for civilian air traffic control.
By setting a special 4-digit code on the aircraft transponder, a pilot can unobtrusively signal a hijacking or other distress condition without having to make an audible radio broadcast.
