IFF Mark II was the first operational identification friend or foe system. It was developed by the Royal Air Force just before the start of World War II. After a short run of prototype Mark Is, used experimentally in 1939, the Mark II began widespread deployment at the end of the Battle of Britain in late 1940.

Identification, friend or foe (IFF) is a combat identification system designed for command and control. It uses a transponder that listens for an interrogation signal and then sends a response that identifies the broadcaster. IFF systems usually use radar frequencies, but other electromagnetic frequencies, radio or infrared, may be used. [1] .

IFF Mark X was the NATO standard military identification friend or foe transponder system from the early 1950s until it was slowly replaced by the IFF Mark XII in the 1970s. It was also adopted by ICAO, with some modifications, as the civilian air …

The IFF MK II was designed to allow switching between any one of 6 different coded responses, usually specified for various types of mission. However, in practice it proved difficult to distinguish one echo from another so generally only position 1 (or A) was used, whilst the longest, widest response position was used universally as a distress ...

Two IFF systems are in use at present by American and British forces. They are: IFF Mark III. Both systems use the same basic components--an airborne (or shipborne) transpondor, and an interrogator-responsor (which in the Mark II system is the search radar)- …

In the Mark II system, friendly aircraft carried a receiver/transmitter which received the pulses transmitted from the radar station and re-radiated them from the aircraft with inappreciable delay and with enhanced strength.

2021年5月30日 · IFF（IdentificationFriend or Foe）系统是指敌我识别系统，起源于第二次世界大战，IFF系统主要通过二次雷达询问-应答协同完成对雷达发现目标的敌我属性识别，防止对“我方”目标误伤。

Identification Friend or Foe is an identification system designed for command and control. It enables military and civilian air traffic control interrogation systems to identify aircraft, vehicles or forces as friendly, and to determine their bearing and range from the interrogator. Collins Aerospace has more than 70 years of experience in IFF.

Mark III IFF, devised in 1940, responded only to special interrogators, comprising low-powered secondary radars using separate antennae operating in conjunction with main radars.

2019年8月22日 · Mode 5 is a military-only identification mode, which modifies the existing Mark XII Mode 4 IFF (referred to as “Mode 4”) system and addresses known shortcomings of the legacy Mode 4 identification mode. Mode 5 will eventually replace Mode 4 and allows National Security Agency-certified secure encryption of interrogations and replies.