I always thought Uhura (prime) was a linguist, she knew many languages and it was part of her job to decode new ones. Thus I was annoyed in STVI when she was portrayed as inept and couldn't even speak Klingon, and really pleased that in STXI Uhura spoke Romulan and was much more than a switchboard operator. We also briefly got to see Cadet Uhura working in the mythical below-decks "communications department", which Nichelle Nichols always liked to tell people about.
But I was told in another thread that there was nothing in TOS or the old movies at all to say Uhura ever did more than open the hailing frequencies and that STXI Uhura's job was redefined to include that of Hoshi in Enterprise.
But I've held my Uhura-is-more-than-a-space-telephone-button-pusher belief for far longer than Enterprise was around. I think I got the idea from old 80's novels, at least one of which had her speak Klingon and others had her decode alien writings and languages.
TOS Uhura: A glorified button-pusher or more?