This Annex Describes principles that shall be used when the calling user specifies information during call set-up regarding low layer capabilities required in the network and by the destination terminal.
Note - In this context and throughout this Annex the term "called user" is the endpoint entity which is explicitly addressed.This may be an addressed interworking unit (IWU) (see I.500-Series Recommendations [51] and Recommendation X.31 [14] case A).