Here you can import all local SIP and IAX (more specific: IAX2) phone extensions that are known to Asterisk, including descriptive names found in Asterisk phone configuration. This will work no matter how complex Asterisk is configured to get the local phones. There is no configuration needed fot this import feature to work.
Only after pressing Import will the selected entries be actually imported into the phone book, pressing Cancel will leave the database unchanged.
Note: New telephone numbers will be added to the phone book database, existing numbers will be overwritten with the new name, all other records remain untouched. If you intend to replace the complete database, you must erase all contents before importing.