asterisk users - Jun 2015 - Getting a list of availabe SIP-Header on phone

Hi list!

I read the pages that Steve sent to the list. It sounds nice, but I  
didn't found any documentation about available SIP-Header on my phone  
(ST2022, not ST2030!).

Is there a possibility to ask the phone which header it understand? Or  
to get this list in other ways?

Thanks a lot
Luca Bertoncello
(lucabert at lucabert.de)