13.2.2 Notification to the Calling Subscriber
23.2843GPPLocal Call Local Switch (LCLS)Release 17Stage 2TS
If the served mobile subscriber has requested that the calling subscriber shall receive a notification about the call forwarding, a notification is sent to the calling party.
If the notification is implemented using intermediate tones or announcements the MSC server requests the MGW to play an announcement/tone to the calling party, as described in clause 14.6, before establishing the call to the forwarded-to subscriber.