Extended in Store Plot Data Options - DTX CableAnalyzer

Enabling this option will extend the frequency of the test selected. It does not change the limit line of the selected standard. 

Store Plot Data for Selected Standards

*DTX-1800 only.
This is also true for Channel measurements.
The feature is found by rotating the dial on the DTX CableAnalyzer to SETUP and selecting Instrument Settings.
Why doesn't Category 6 / Class E run to 900 MHz on "Extended"?
These standards are available in the DTX-1200, a 350 MHz tester. The concept behind "Extended" is to run the maximum frequency whilst keeping it simple. Extended on the DTX-1200 and DTX-1800 is the same for the sake of simplicity.