What they squawked was what they dialed in for an ID
in mode 3 to let know who they are.
Mode 4 IFF is automatic and not under their control.
IFF stands for Identification Friend or Foe.
I guess they are up to mode 5 now.
better encryption.
SIF is for civilians.
Come on bro, I was an air traffic controller for 20 years. I know what it all means. You said SIF (selective identification feature) was for civilians. Not true. The F-4s and F-111s at Mountain Home had it. All the aircraft in Vietnam had it. By then, even the C-47s had it, even though it was only two digits, like 04. When I got to Laughlin, the T-38s had 4 digit codes, like 7500. We used only mode 3. I don’t even know what the other modes were used for. I didn’t much care. I only wanted to get them on the ground.