Call completion can be used to monitor a busy number.
•Both devices are connected to the same PBX
•The PBX supports SIP Subscribe (BLF)
•Telephony > Call signalling > Call Completion
•Settings > Telephony > Call Completion
1.You call a subscriber and hear the busy tone.
2.Press the appropriate soft key to activate the automatic callback.
3.A notification is displayed as soon as the called number is no longer busy.
4.Confirm the notification to call the subscriber, who is now free.
5.The callback process is then deleted in the PBX.