In ______. [originaltext] Television, which made its first serious appearance

Television, which made its first serious appearance in 1939, did not become common until the early 1950s. Since then. millions of children have grown up in front of the set, and many people now worry about the effect that TV has on the young, and on society in general. Many ordinary parents wish it had never been invented.
   Like almost anything else, television has its good and its bad sides. One should surely thank its inventors for the joy and the interest that they have brought into the lives of the old, the sick. and the lonely --all those who, without it, would have no pleasure and no window in the world.
   In truth, television has opened windows in everybody’s life. No newspaper has ever reached so many people and shown so clearly what is happening right now in their own country and everywhere else. TV has transformed information. It not only gives the news instantly, but also shows it in pictures--more powerful than words. It can be said that TV has brought reality to the public.
At what time did television become common?