Hey DL, whilst stationed at Leuchas I had occasion to visit Ferranti's factory. I can't remember as to why now but I did have the opportunity to question one of their designers re A.I.23/B attack radar fitted to Lightnings. My question was, 'In the equation relating to all inputs to the analogue computer, there are elements a and b. What do they refer to and where do they come from?' (or something like that). His reply was, 'We don't know, they're just there. ' Well, whatever they were, the radar worked very well, especially when you know that there wasn't a single soldered joint in it.