This military system is called IFF (Identification Friend or Foe).

The contributing factors were a lack of an "Identification Friend or Foe" transmitter on the helicopter and poor communication between the army and navy.

The antivehicle batteries functioned automatically, irrespective of the target's Identification Friend or Foe signal.

Sharon had sent out an IFF (Identification Friend or Foe) signal, to which only friendly aircraft would reply.

Mode 4 is used by military aircraft for the Identification Friend or Foe (IFF) system.

The e-TAG tolling is based on a modified Identification Friend or Foe system.

The Identification Friend or Foe highlighted each plane's position on the controller's radar.

Not included are additional military (or IFF) modes, which are described in Identification Friend or Foe.

"The next Identification Friend or Foe code is due in a week," the computer said.

This gave a pinpoint position, estimated height and number of aircraft and whether Identification Friend or Foe (IFF) was indicated.