Panasonic KX-TVS50 Installation Manual page 64

INTEGRATING THE VPS WITH PANASONIC KX-T PHONE SYSTEMS
c)
Assignment of IRNA (Intercept Routing No Answer) timer:
1)
Go to the "2-4 System Timer 1/2" screen.
2)
Assign "Intercept Time" parameter.
3)
Click "Apply" to save the changed data.
Note:
This parameter tells the KX-TD500 how long to let a call ring at an extension
before forwarding (redirecting).
Screen output:
64 Installation Manual