There is full documentation in Nortel Bulletin P-2008-022-Global-Rev1, Dated 28 February 2008
The title of the Bulletin is:
UNIStim Firmware Release 2.2 for IP Phones, including 0604DBN for Phase II IP Phones (2001, 2002 & 2004), 0621C4T for IP Phone 2007, and 0623C4L, 0624C4L, 0625C4L and 0627C4L for IP Phone 1110, 1120E, 1140E and 1150E respectively