This procedure describes how to calibrate the media sensor on an S One.
EDIT : Since firmware Rev. 6, it is no longer required to enter service mode to perform the media sensor calibration.
It can now be found in User mode under Settings>Calibrations>Media Sensor Setup.
Link to the video tutorial : https://summamail.sharepoint.com/:f:/s/SummaTechnicalSupport/EgnFXegdpkFNj7YGTYdDpWIBvjmcHZ4EfLc7ChD7nnEV6Q?e=W0qagW