Quinton TM55 Service Manual page 13

A grade potentiometer senses the rack gear movement for the grade
system feedback. Limit switches limit the travel of the rack gears in the
event of a potentiometer failure or incorrect calibration.
Deck and Roller Assembly
The deck and roller assembly provides the running surface for the user.
This surface consists of a movable and flexible walking belt supported by
a semi-rigid platform. This platform is supported by a steel-welded frame.
A poly-V drive belt, coupled through a pulley to the drive motor, drives
the front roller. The front roller uses friction to drive the walking belt. A
rear roller, acting as an idler pulley, tensions the walking belt. Both rollers
are mounted to the steel support structure.
Cardiac Stress Treadmills Service Manual Theory of Operation 2-3