TV isn't very good about matching phones with their real sounds. How many shows have you seen where someone uses a pay phone and when they insert the money it goes "ding-ding?" Ding-ding went out with the demise of the three slot payphone (around the middle of the 60s.) I'm guessing that most people casually wouldn't have a clue that the ringing of a phone's sound was wrong. How many times have I seen a show with a 2554 wall phone that rings with a dual gong ringer sound? Plenty!