EXFO FTB-500 (Window XP) - Manual (Page 279)

Troubleshooting
FTB-500 269
Solving Common Problems
My module does not seem
to fit all the way inside the
platform and I cannot lock it
in place using the retaining
screw.
You are using an older
module with a rubber O ring
directly behind the
faceplate.
Remove the O ring simply by
pulling it away from the
module. The O ring will be
permanently removed, but
this does not affect the way
your module will perform.
Your module also remains
fully functional on the other
EXFO platforms
Problem Possible Cause Solution