How to turn off ringer at particular extension?

Do Not Disturb (DND)
When DND is enabled, the telephone will not ring when someone calls, but the line

indicator still flashes. In Personal Call Manager, the
You Have a New Call dialog box
still appears and the icon for the call appears in the Calls box.
You can turn the Do Not Disturb (DND) feature on or off from the
Calls menu or the Personal Call Manager icon in the task tray.
Turning DND on or off
To turn DND on or off:
1. Click the Personal Call Manager task tray icon or the
Calls menu.
2. Click the DND menu item.
When DND is on:
• the Personal Call Manager task tray icon changes to
• the symbol check
appears beside the DND menu item on the Calls menu and the
Personal Call Manager task tray menu
• DND appears in Status bar