Section: 5.5.1 In-band tones and announcements
Content: When the network wants to make the mobile station attach the user connection (e.g. in order to provide in-band tones/announcement) before the mobile station has reached the "active" state of a call, the network may include a progress indicator IE indicating user attachment in a suitable CC message: - Either it includes the IE in a SETUP, CALL PROCEEDING, ALERTING, or CONNECT message that is send during call establishment - it sends a PROGRESS message containing the IE. A progress indicator IE indicates user attachment if it specifies a progress description in the set {1, 2, 3} or in the set {6, 7, 8, ..., 20}. On reception of a SETUP, CALL PROCEEDING, ALERTING, CONNECT, or PROGRESS message the mobile station shall proceed as specified elsewhere in clause 5; if the progress indicator IE indicated user attachment and a speech mode traffic channel is appropriate for the call the mobile station shall in addition: attach the user connection for speech as soon as an appropriate channel in speech mode is available. (If a new order to attach the user connection is received before the attachment has been performed, the new order shall supersede the previous one.) Under certain conditions the MS will have to attach the user connection before the CONNECT message. It is up to the network to ensure that no undesired end-to-end through connection takes place during the establishment of a MT call. NOTE: This allows the use of progress indicator IEs independently from the channel modes appropriate for the call. The network may generate multimedia CAT to a mobile station supporting multimedia CAT during the alerting phase of a mobile originated multimedia call establishment as specified in subclause 5.3.6.4.