Panasonic KX-TD500 System Reference Manual page 284

4) Call Transfer and Voice Mail Integration
Not only an incoming call directed to the extension, but a transferred call
(both screened and unscreened call transfer) is also applied to the Voice
Mail Integration feature.
Camp-on Transfer to a VM extension and Transfer Recall
Example
VM.108 (busy) VM.107 (busy)
Hunt
Ext.100
Making a
call
1. The Ext.100 makes a call to the Ext.101.
2. The Ext.101 answers the call from the Ext.100 and transfers it to the
Ext.102 (Call Forwarding – All Calls to VM 106 is assigned). Then
replaces the handset.
3. Since FWD destination VM.106 and all other VM extensions in the
Station Hunting Group are busy, the call from Ext.100 is put on the
waiting status.
<Camp-on Transfer to a VM extension>
If VM.106 becomes idle before the transfer recall timer has been elapsed,
the call is connected to the VM.106, and the caller can access the
mailbox of the Ext.100 automatically.
Camp-on Transfer to a VM extension is only available when "Call
Forwarding–All Calls" is assigned to the Ext.102.
<Transfer Recall>
If VM.106 is still busy after the transfer recall timer has been elapsed, the
call arrives at Ext.101 again.
What if Call Forwarding (FWD)-No Answer is assigned on the
extension where a call has been transferred without announcement
(Unscreened Call Transfer) ?
A call is forwarded to the FWD destination after the Call Forwarding No
Answer timer has been expired.
If the FWD destination is busy, the forwarded call arrives at the extension
who transferred the call again.
(Note)
In this case, if the destination of Call Forwarding-No Answer is an
Attendant Console, the transferred call is not forwarded to an Attendant
Console.
The transferred call arrives at the extension who transferred the call after
the Call Forwarding No Answer timer has been expired.
3-F-24
VM.106 (busy)
Hunt
Ext.101 Ext.102
Transferring
a call
FWD
FWD–All Calls
to VM.106