<prompt> Translate the following text to EnglishMabadiliko makubwa ya utangazaji wa umma yalitokea katikati ya miaka ya 1970, wakati mashirika ya Marekani yalipoingilia kati kujaza pengo la kifedha kwa mtandao wa chini wa fedha.  <response>: Public broadcastings big transformation came in the mid-70s, Ledbetter finds, when U.S. corporations stepped in to fill the financial gap for the underfunded network. 