Yup, that's the one.
I would immagine that it works on a pilot sw. set up, and operates on a regulated air supply, hence delivering the same amount of 'force' with each 'hit'.
Should the supply of air go below a certain pre-determined pressure, the pilot valve would not operate, thus preventing the trap from cycling on too low a pressure.
Just assuming, but that's how I would see it working, or at least, that's how I would configure it to work.