Varian Associates specified potentiometers for the positioning requirements of its radiation-therapy equipment because the components are robust, withstand radiation, and are less costly than encoders. Potentiometers were selected in place of other position sensors because of their inherent radiation hardness. The less expensive potentiometers, on the other hand, can easily withstand a million units of radiation. The jaws can define fixed apertures from 0.5 cm to 40 x 40 cm. They can also be moved dynamically during exposure to modulate the beam's intensity in a process similar to the dodging and burning used in photo processing.
Spur gears link the potentiometers to the aperture-control motors.
In order to withstand high shaft side loading, these potentiometers are equipped with ball bearings. Other potentiometers control the rotation of the collimator, the machine's gantry location, and the orientation of the couch upon which the patient lies. Potentiometers are also used to control the rotation of the aperture head and the entire beam section. During the transition, Bard's manufacturing capacity was to be relocated to the Arrow facility in Everett. In order to almost triple capacity, a new production room needed to be built.