backpack pump question?

as people know weve been talking about the pumps in diy trolleys turning themselves off after they get to a certain pressure and how these £15 ebay jobbies dont do that so wondered how do the back packs work like gardiners etc, do they have a pressureswitch etc or just keep pumping like the ebay ones and releases pressure somehow?

I've got the big boy and use an aquadapter with it and the pump in that stops pumping when the flow is stopped.

I think it is only a 60psi pump though so whether that has anything to do with it or not I don't know.

Best way is just to use a remote to cut the power to the pump then you don't have anything to worry about.