The SP 9010 group are looking for one of these, used to activate Automatic Train Stop. I am curious if any of these survive in museums, if nothing else at least one should be saved for posterity, ATS was an important development (from their facebook page):

"This is the "Duplex Magnet Control Valve" -- part of National Safety Appliance Company's Automatic Train Stop (ATS) system, used by the Southern Pacific Railroad from the 1920s to the late 1960s and a distant precursor to today's Positive Train Control.

When this valve and its ski-like "Inductor Planes" passed over an ATS track magnet in proximity to a restrictive block signal, if the engineer didn't respond correctly to the track signal the valve would activate the train brakes. The system was deployed over Donner Pass and on parts of California's Western Division between the Bay Area and Sacramento.

SP 9010 arrived from Germany with no ATS in place, but with the air system and schematics ready to accept. SP Shops in Sacramento installed the system in May of 1964, with KM resident technicians in attendance; it took more than one scheduled day to turn out the unit. The ATS system was abandoned by SP in the latter part of the 1960s, and SP 9010's Duplex Valve was removed and presumably discarded.

And that brings us to 2020.

In the twelve years since beginning this restoration, we have been unable to locate an ATS Duplex Control Valve. Hundreds were applied, to steam and diesel locomotives alike -- and we've not seen one remaining in captivity. There are many surviving SP locomotives with the bracket, the ATS double-heading valve, or the Engineer's cab-mounted "forestalling" answer valve and plumbing still in place. But nowhere have we been able to find a preserved Duplex Valve.

As has been proven with many other missing SP 9010 items, we think one may be yet prove to be out there -- but we need your help to find it!

Our mission in its absence will be to build a non-working replica, since the area under SP 9010's pilot seems to be yearning for that absence to be corrected.

Do you know of one in a collection somewhere? Even such that we could borrow or photograph for research and patternmaking? If you do, please contact us through the SP 9010 website -- and thanks!

Contact Link: http://sp9010.ncry.org"