Panasonic KX-TDE600 - Busy Line;Busy Party Features; Automatic Callback Busy (Camp-On)

Feature Guide References
1.1.3.3 Call Waiting
User Manual References
1.2.4 When the Dialled Line is Busy or There is No Answer
1.8.3 Receiving Call Waiting (Call Waiting/Off-hook Call Announcement [OHCA]/Whisper OHCA)
Feature Guide 123
1.8.4 Second Call Notification to Busy Extension