The present invention relates to a user equipment device of a UMTS
(Universal Mobile Telephone System) type mobile radio telecommunications
system. The user equipment device (UE) works selectively in two modes of
operation, a connected mode in which resources of the system are
allocated to setting up a connection with the user equipment device and
an idle mode. The user equipment device is identified in idle mode by a
first identity (IMSI; TMSI; PTMSI) and in connected mode by a second
identity. According to the invention, the user equipment device in
connected mode is capable of processing messages in which it is
identified by its first identity (IMSI; TMSI; PTMSI).