I do not know if the KH telephone exchange ever existed, or if the appearance of KH1-7400 in this scene is meant to represent a phone number. It certainly looks like a telephone exchange name number, KH does not appear in the Telephone Exchange Name Project's Database or at phone.net46.net, which are the only 2 sources I refer to for this project. "Taxi Driver" did show a MUrray Hill exchange name number in another scene, which I think illustrates that Martin Scorsese did not have any kind of directorial policy of using bogus phone numbers in the style of modern film-makers.

UPDATE: AUGUST, 2012: THE NUMBER IS REAL. [URL=http://sorabji.com/pictures/Telephone_Exchange_Names/Movies_and_TV/2012_08_12_18_00_03.jpg.html]READ ABOUT IT HERE[/URL].

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