I'm fairly sure that the programme selection for the AI23B/C/D on the indicator was 1 for Firestreak and the others for Redtop. I also vaguely remember that one of the functions of the Computer Red was to determine the closing speed and send the appropriate signal to the missile to fuse it for a head on or a tail shot. I was also told that Red Top would delay it's explosion on a tail shot to try to ensure it got the crew as well as the airframe. Never was quite sure if the plumbers were shooting their own line on that one!
pmills575
ex Air Radar on AI23