Editing ISDN User Part (section)

=== ITU-T specification versions ===
* 1980 – ISUP Yellow Book
* 1984 – ISUP Red Book
* 1988 – ISUP Blue Book
* 1991 – ISUP Q.767<ref name= "q767">{{Citation | url = http://www.itu.int/rec/T-REC-Q.767/en | publisher = ITU-T | title = Recommendation Q.767}}.</ref>
* 1992 – ISUP'92 White Book (segmentation, compatibility, new supplementary services)
* 1997 – ISUP'97 (new procedures, IN CS1, new supplementary services)

According to ITU-T Q.761 section 2.4.1 ''ISUP interworking'' ISUP'92 is backwards compatible with ISUP Blue Book and Q.767<ref name = "q767"/> for basic call procedures and supplementary services except for some procedures (e.g. number portability).<ref name = "q761">{{Citation | url = http://www.itu.int/rec/T-REC-Q.761/en | publisher = ITU-T | title = Recommendation Q.761}}.</ref> Additionally the compatibility features introduced in this version ensure forward compatibility with newer versions.