IFF transponder MK 3 g
This American transponder is for automatic identifying friendley or ennemy aircrafts. The transponder in one aircraft, sends a coded signals to the unknown aircraft. This aircraft, is responding then with another coded signal. If well detected , it is identified then as a friendly aircraft.
Above my BC966a IFF mk3G transponder. This was an earlier type. Note the coaxial cable from the transmitter to the receiver part.
The two pictures above is the control-unit BC958a from the transponder. Just under the green metal plate, the destruction switch is hidden. When the aircraft would fall into ennemy hands, for instance it was hidden by ennemy fire on his mission, you could let explode a little detonator inside the transponder for destructing the coding system inside. IFF was most secret.
The remote controll units. Left the type 965, right the type 985.