2-1 Alternating

The most common type of alternating which every other air cell alternates during each alternating cycle. 

3-1 Alternating 

(US Patent 6,152,176A since 1998; Taiwan Utility Model Patent 153420)

3-1 Alternating is a type of alternating that alternates every other 3 air cell during each alternating cycle. In each alternating cycle 33 percent of the mattress is deflated and 66 percent is inflated, therefore the patient is resting on a larger surface area and will be more comfortable and feel less of the gaps comparing to 2-1 Alternating.