Valve Pilot?

[train18393]

I was reading the spedometers in steam engines and I had mentioned the Valve Pilot the NYC and many other railroads had in at least their large steam engines. I know there was also some sort of Valve Pilot brake valve involved if the speed limit was exceeded that had to be manually reset from outside the cab. There was a box on the engineers side of the locomotive by the valve gear frame, also the speedometer in the cab indicated the Valve Pilot corp on its face and from what I understand it also recorded the locomotives speed. Can anybody provide me more information. My Locomotive Cyclopedia is not to specific, but just indicates that speedos and valves etc are available from the Valve Pilot Corporation, but no explination of how any of it works.

Thanks in advance, Paul

Dayton and Mad River (HO) railroad

[BaltACD]

Picture is of a RF&P steam engine....the box with printing on it on the engines pilot is it's Automatic Train Control equipment box.  ATC receives signals from the track circuits that the train is operating on....the information from the track circuits mimic the signal indications displayed on the wayside signals....as long as the train is operated in conformity with those signals....nothing happens.  If the train operates at a speed faster than allowed by the signals, the ATC takes over and stops the train.  ATC has been in effect on the RF&P since the middle 1920's and is still in effect on that piece of railroad today as the RF&P Subdivision of CSX.