A collection of electronic equipment used by the Royal Air Force during the Second World War, including: A Type 50 wireless modulator unit and Type 39 wireless transmitter part of radio homing beacon used at ground stations by Royal Air Force Coastal Command; A Type 25 cathode ray tube, a Type R3121A wireless receiver transponder and a AN/APX-6 wireless receiver transponder and Type CZR-23ABH selector unit for ABK-5 receiver transponder, all parts of IFF Mark IIIG unit.
IFF(Identification, Friend or Foe) Mk III
(See COM 1002 for the early British development of IFF )
The proliferation of radar frequencies, including
microwave frequencies, and the impracticability
of continually adapting the operational IFF Mk II
system, led to the development of IFF Mk III.
The British scientist F C Williams conceived the
idea of a ' Single Band IFF' using a universal
interrogating system, one independent of the
primary radar frequency. The new IFF system
would respond to a special interrogating
transmitter and not reply directly to radar
signals.The interrogation took place on the 1.6 to
1.9 metre range which the IFF transponder
swept,and transmitted a reply on the interrogative
The basic design was ready in early 1941, and
production began with Ferranti Ltd.The first large
scale demonstration of IFF Mk III took place in
Britain in late 1941, and American observers
were present. After some debate , the IFF Mk III
was adopted as the Allied standard during the
war. Production began in America in 1942 with
the Hazeltine Corporation.
IFF Mk III was fitted in RAF, Fleet AIr Arm, USAAF
and USN aircraft , and deployed world wide.