Internal help for this application in Asterisk 1.4: 

  -= Info about application 'SetTransferCapability' =- 

[Synopsis]
Set ISDN Transfer Capability

[Description]
  SetTransferCapability(transfercapability): Set the ISDN Transfer 
Capability of a call to a new value.
Valid Transfer Capabilities are:

  SPEECH             : 0x00 - Speech (default, voice calls)
  DIGITAL            : 0x08 - Unrestricted digital information (data cal
ls)
  RESTRICTED_DIGITAL : 0x09 - Restricted digital information
  3K1AUDIO           : 0x10 - 3.1kHz Audio (fax calls)
  DIGITAL_W_TONES    : 0x11 - Unrestricted digital information with tone
s/announcements
  VIDEO              : 0x18 - Video

diff output to internal help in Asterisk 1.2: 

17c17
<   VIDEO              : 0x18 - Video
---
>   VIDEO              : 0x18 - Video: