From the Ultimarc website Minipac page,
"Trackball/Spinner Functionality
In USB mode only. No extra PC connections are needed, all communications go through one USB cable. Inputs for one 2-axis device (trackball) and one single-axis device (spinner). The active control is auto-selected when one control is moved after a 10 second idle period. If trackball/spinner are used, USB mode must be used for all controls. The full wiring harness for 28 switches and optical controls is available in two versions, for either Happ or Ultimarc trackball.