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IFF: Identify Friend or Foe

Identify Friend or Foe is a device that allowed allied aircraft to identify themselves as friendly when they were coming in from enemy airspace. This prevented incidents of friendly fire, in which the British anti-aircraft gunners were forced to attack incoming allied aircraft because there was no way to determine if they were friend or foe.

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The IFF transponder on an incoming allied aircraft receives a signal from a Chain Home station. An oscillator in the IFF system responds with a ringing at the same frequency, which is then received by the Chain Home station. The signal registered as a distinct “blip” on Chain Home display screens, which indicates to the operator that the incoming air craft is friendly and should not be fired upon.  

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Disclaimer: The audio files available on this virtual exhibit are the result of a long term oral history interview project conducted by the Secrets of Radar Museum. Sections of these interviews have been compiled here to make them accessible to the general public. Interviews were conducted by different museum staff at different times using different recording devices. As a result, some of the audio clips have background noise or other imperfections. The Secrets of Radar Museum has worked to ensure that the recordings shared here have been refined to increase sound quality and reduce these imperfections, but some recordings will still have flaws due to the limitations of the original audio file. The Secrets of Radar Museum appreciates your understanding in this matter. Please contact us for more information.

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