The 1000, 3000A, 4000 and 9000A have a user configurable high voltage limit.
This can be set to limit the maximum voltage that the calibrator is capable of outputting for safety reasons.
To perform this, first make sure that the Transmille Calibrator Setup Utility is downloaded and installed on your computer (Support Link)
Connect the calibrator via USB and start the Calibrator Setup Utility, and click on 'Settings'
On the settings window that appears, navigate to 'High Voltage Output Limit'
Type in the maximum voltage as desired in terms of Volts, without the units. The default limit is 1040.