User Port Unavailable Message UPU
user-defined-message function
User-to-User Information Message
USR (User-To-User Information Message)
USER User System EvaluatoR
User-User Signaling UUS
SSCOP User-to-User Information
User-to-User Indicators
User-to-User Information
user-to-user interface level
user-to-user signalling (UUS)
UUI User – to – User Indicators
UUI User C to C User Indicators
UUI User to User Information