Open the instrument shoe (read switch must NOT be closed).
Remove the AC adapter (if attached).
Press the power switch turning the instrument off.
Simultaneously press and hold the 'X' key and the 'DOWN ARROW' key.
While holding the 'EXIT' and 'DOWN ARROW' keys, press the power switch a second time.
In approximately 10 seconds the instrument will display the following message:
Been restored OK
Press the 'ENTER' key to return to normal operation.
Finish by performing a full calibration