If anyone is interested in the history of long-distance telephony in the US, the PBS documentary "Transistorized!" (http://www.imdb.com/title/tt0381663/) (https://www.youtube.com/playlist?list=PLA97634694AC92A93) has a great explanation into Bell Labs' long-standing interest in the transistor going back to the use of vacuum tubes in signal amplification on the long stretches of telephone cable. The documentary is also really cool since it shows you the inner lives of Shockley, Brattain and Bardeen leading up to the discovery.