Section: 5.2.1.4.2 Call progress in the PLMN/ISDN environment
Content: In order to inform the mobile station that the call is progressing in the PLMN/ISDN environment the network may send a progress indicator information element to the calling mobile station either: a) in an appropriate call control message, if a state change is required (e.g., ALERTING or CONNECT); or b) in the PROGRESS message, if no state change is appropriate. This progress indicator information element shall contain progress description value #32 "Call is end-to-end ISDN/PLMN". See also subclause 5.5.6 for further reactions of the mobile station.