- Low-gear air tube 
- High-gear air/oil tube 
- High-gear proximity sensor . This sensor is normally open (initially de-energized).
- Low-gear proximity sensor . This sensor is normally closed (initially energized).
- Gear-shift piston 
- Inputs column on diagnostic screen .
This video shows how the gearbox changes gears:
- The control sends air to the low  or high-gear tubes .
- The low-gear  air tube sends air to the gear-shift piston , or the high-gear  air/oil tube sends oil to the gear-shift piston .
- The gear-shift piston moves into the correct position.
- The proximity sensors [3 and 4] read the position of the gear-shift piston .
- The DIAGNOSTIC page on the display  shows if you are in low or high gear.
The low gear and high-gear proximity sensors behave differently:
- The high-gear proximity sensor  is normally open. In high gear, the piston shaft does not engage the proximity sensor.
- The low-gear proximity sensor  is normally closed. The piston moves down to engage the high-gear  proximity sensor, and then the low-gear  proximity sensor.