Postwar broadcast coverage was extended to Birmingham in 1949 with the opening of the Sutton Coldfield transmitting station, and by the mid-1950s most of the country was covered, transmitting a 405-line interlaced image on VHF.[original research?]
What kind of image was broadcasted by the BBC by the mid-'50s?
{'text': '405-line interlaced image', 'answer_start': 194}