The telephone userpart (TUP) is the first SS7 user part defined by CCITT. An early version appeared in the 1980 CCITT Yellow Book. The 1985 Red Book and the 1989 Blue Book include a number of additions and modifications [ 11. The term “telephone” dates back to the beginnings of the TUP development, when all calls were “speech” calls. The calls in the present telecommunication networks can also be used for facsimile, and other data communications.