Paul Ewing has kindly given me some pages of BBC Engineering Information Dept material explaining Test Card C. I know that out in the world there used to be a whole cult (is that the right word?) of test card appreciators. They’d write to Presentation asking about the music, and of course, to EID about the vision……
I have to say, though, that the bit I like best is this next – a compliments slip from EID. The first communication I ever received from the BBC was a copy of Technical Careers in the Engineering Division, and it came with one of these. I still have it somewhere.