Very good. Full details of the development of Test Cards J and W here, which I read years ago and thoroughly enjoyed: https://web.archive.org/web/2010012310275

Very good. Full details of the development of Test Cards J and W here, which I read years ago and thoroughly enjoyed: https://web.archive.org/web/20100123102758/http:/www.barney-wol.net/video/testcardw/testcardw.html https://web.archive.org/web/20100123102758/http:/www.barney-... Also, Richard Russell's page here: https://www.bbceng.info/Designs/designs_reminiscences/richard_russell_part2/rtrbbc.html https://www.bbceng.info/Designs/designs_reminiscences/richar... who did the technical work.