Automatic tire inflator keeps pressure constant

Its not something new, Seen it on big rig trailers, the government had it on some of the heavy duty missile trailers,and GM had it on some Hum Vs. Neighbor showed it to me on his hummer. Different design not a pump. Air went to the axle /hub and pin holes, in the hub let air into the wheel assy. This seems to be a lot better system.