Philips CDD522 Operating Instructions Manual page 36

However, it is important to note that the FINAL FIXATE command
will not write a special pointer to the next session in the lead-in of
this last session. This indicates to the CD-R that no more
Sessions may be added after this last one.
If the user wants more information added, e.g. Photo-CD where a
new load of photos from the last holiday must be added to those
of previous trips, the FIXATE command must be used instead.
During FIXATION, the Lead-in is written to the disk with a pointer
to the start-position of the next Session (that does NOT have to
actually exist). In the same action, the Lead-Out is written to the
disk with a pointer to its own Session-start.
To summarize:
The user wants to record a Session, and to leave open
the possibility to record another after this one: the
FIXATE command should be used to make the disk
Red/Yellow/Green Book compatible.
The user want to record a Session, and does not ever
want to record another Session after this one: the
command used should be FINAL FIXATE.