"Ed Rasimus" wrote

Foggy memory trying to recall things. Best I recollect (although I
might be wrong) was that the IFF/SIF had cockpit control of modes 1,
2, 3 and C. Don't recall that Mode-4 was cockpit controllable. In the
F-4 the coding was done in the nosegear well on the ground with a
plunger-like device.

Trivia alert

Probably had a "zero, a/b, hold switch", and a caution lite. there was two
codes a-today b-tomorrow, and the hold kept your plunger data on a hot turn, while the
caution lite blinked when someone interrogated you, but your box
couldn't decode it, and it stayed on solid if you lost your crypto (plunger data) or
the computer went TU.

Usually the blinking lite is the worst, because it means the Patriot battery is now
trying to figure out a second way to ID you