[jacquesm]

They're simply 12V solenoids with an air valve attached, to that I've run a small 1/8th" tube to a piece of thin copper tubing that's open on one end. Nothing fancy or branded, the air valves are all attached to a manifold that divides the pressure from the compressor across all the valves.

12V on the valve -> air streams out of the corresponding tube.

[sprocket]

Ah, yes; it was the manifold that I was looking at and wondering what it was. Thanks for the explanation!