EXFO FTB -5240S/5240BP Optical Spectrum Analyzer for FTB 500 (NS-1434) - Manual (Page 152)

Setting Up the Instrument in Drift Mode
144 FTB-5240S/5240BP
Setting Up Drift Analysis Parameters
5. Modify the settings as needed. For more information about the settings,
see Adding Channels on page 137, Changing Default Channel
Parameters on page 309 and Defining Channel Thresholds on
page 132. If you leave a box empty, it will remain as it was before your
changes. Modify appropriate settings.
6. Press OK to return to the Channels tab, which now contains the
modified settings.
7. Press OK to save the changes and close the window, or press Cancel to
exit without saving.