Originally Posted by
Rhino power
Sidewinder seeker heads are passive, no need for any 'air to air kit' other than the necessary wiring and the switchology in the cockpit, lock-on is confirmed by a tone in the pilot's headset...
-RP
I don't actually know much about the Sidewinder development but the tone was a genius idea. Much easier to integrate into the cockpit. I'm guessing the tone is an almost direct feed from the seeker head circuit.
I'm sure today's Sidewinder doesn't even have a seeker head like the original and the tone is generated but ok.