Other topics about Setting Control Functions
The software options can be purchased separately to enhance the E4990A measurement functionality. When you purchase the software option upgrade kit, Keysight provides the software entitlement certificate.
Get the license number at http://www.keysight.com/find/softwarelicense.
Press System > Service Menu > Enable Options, then select option which you want to activate.
Type the relevant 12 character long license key sent by Keysight in Key Code entry dialog box, then click Enter.
Restart the firmware or reboot the instrument.
Check the installed option at Product Information
The license key for some options are kept in a text file (.lic) located at Factory(E:)\LICENSE\. The E4990A refers to the license codes in all of .lic files under the directory.
When you change the storage, copy the .lic files as back up. You can re-create the license number at http://www.keysight.com/find/softwarelicense with your software entitlement certificate if the option is added with the upgrade kit.