Did the F-106 use the D/L ? How did the IRST with the -102 work, please ?

Yes, the F-106 used data link extensively. See my video about the SAGE system. The IRST infrared search and track system in the F-102 and F-106 was a cooled seeker head which scanned left and right, and we could move it search up and down. It would give a "blip" when it saw something. The cooled seeker meant that it tended to avoid things like natural background heat sources, but the sun is a great source of infrared energy and sun reflections on clouds produced strong infrared signals. The moon also produced an infrared target. There was no indication of how far away the target was, just the angle to the target. With the angle, you could turn toward it and go fast and you'll probably catch it. You could slave your radar to the infrared, so the radar beam would be right on the target and you could get a radar return. Radar would then give you range to the target. This was effective against electronic countermeasures, which would foul up the radar in various ways. With the IR lock-on, the radar would look directly at the target and ignore lots of ECM, and would "burn through" the ECM as you got closer. With the radar giving range information, you had a very good probability of kill. If your radar was not working, you could fire your IR missiles without radar range. I did that personally on a live fire once, but was closer than I thought to the target -- the small drone looked very small, and when I fired the IR missile blew up the drone and I was too close, and had to fly right through the fireball. Fortunately, no big pieces hit my plane - I had only a few scratches on my paint.

- Could the IR Missile seekers be slaved to it ?- Why was the Falcon that unreliable ?

Yes, the IR missile seekers were slaved to the IRSTS or to the radar, as chosen by the pilot. Reports of unreliability of the Falcon are wrong. The F-4 did not have the MG-10 or the MA-1 systems to control the Falcons, so the problem was with the F-4, not with the missile!

And where was the switch for it ?

I went to the same school in 1956 and then to Youngstown Municiple Airport. We had F-86Ds until our Deuces were delivered. Unfortunately the Air Force was moving senior Sergeants into our career field because they figured they would stay in. We had almost no opportunity for promotion. We were given a choice of going to Thule in Greenland or an early out. They lost 97% of our shop. We had good times. Did you ever find a big enough screwdriver to work the upper electronics bay?

That and it's primary missile armament being the AIM-4 which has its fair share of reliability issues.

The MA1 system followed the F-102 MG-10 system. The MA-1 system was the new Digital based system that came in the F-106. I worked 9 years on the MG-10 on F-102's but never had the chance to move on to the F-106 MA-1 digital system. Must have been a neat system!