looks similar to this:
http://patimg1.uspto.gov/.piw?Docid=...y=7540D3BEC086
Eben, it has 3 fittings on it and then 2 outlets to the plenum that go to the air piston... one fitting is the main air in, then the other two go into the switch side inside the plenum....air on the main side, 13 vac on either side of the solenoid depending on if either the limit swith or the foot pedal is pressed puts voltage on one side or the other....brass case is ground to the machine.. thing clicks, feel air exhausting out of the small port in the top which I assume is an exhaust port, but no air goes to the piston through the plenum cuz it doesn't move anywhere....I can take a rubber tipped air nozzle and push it into the holes for the air piston and make it move back and forth, but it doesn't work through the solenoid... here's what the whole thing looks like:
http://www.powerdrives.com/schrader_...s/overview.htm