Other topics about Setting Control Functions
The software options can be purchased separately to enhance the E4991B 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.
Check the installed option.
The license keys are kept in a text file (.lic) located at Factory(E):\LICENSE\. The E4991B refers to the license codes in all of .lic files under the directory.
If there is no required license code in the .lic file, an error occurs and the E4991B measurement application works as simulator mode only.
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.