No, it's fixed within the Partner system.
From Ext. 10:
Feature 00
Left Hand Intercom button Twice
Right Hand Intercom button Once
Dial the extension number of the phone you want to change
The Lines light up
Solid = Immediate Ring
Slow Flashing = Delayed Ring
Fast Fluttering = No Ring
Press a Line button to toggle the ringing mode - for instance, if a line is set to Immediate Ring (Solid), pressing that line one time will change it to Delayed Ring (Flashing), pressing a second time will change it to No Ring (Fluttering), and pressing it a third time will take it back to Immediate Ring
Once the lines on the extension are set the way you want, press the Right hand Intercom Button once, and either dial another extension number to program, or press Feature and dial 00 to exit