Panasonic KX-TVA594 Installation Manual page 145

c)
Program the PBX so that it will direct overflowed calls to the VPS.
1)
Go to the "Groups-VM (DTMF) Group-System Setting" screen.
2)
Select "None", "Answer by Mailbox", or "AA" as the parameter for "Intercept Routing
to the VPS Sequence".
This parameter determines which DTMF command the PBX will send to the VPS in
order to select the desired service (AA, VM, Custom Service, etc.). If using a Custom
Service, select "None".
3)
Click "Apply" to save the changed data.
5.3 KX-TDA and KX-TAW Series PBX Programming for Inband Integration
Installation Manual 145