If you have multiple line registrations, hitting "Do Not Disturb" on your phones will bring up a menu to choose which line you wish to DND, with "Set All" and "Clear All" being options. For each line listed in the menu "Disabled" means that DND is off, ...
probably requiring an understanding of the ancient culture itself to understand, and at worst fragmentary to non-existent, all because when it was created, that language was commonplace, and therefore writing down proper instructions would have enabled anyone to get in. ...