It looks like you're describing the brake valve cut-off valve. This is a three position valve that sets the automatic brake valve for different functions.
"Pass", "Frt" and "Out".
"Pass" is the position when hauling passenger stock with graduated release valves. You prolly know by now that the brakes can be put on in increments, a little bit more each time until they are fully applied. To release them you move the brake valve into the release position and the brakes are fully recharged and released. You can't take the brakes off bit by bit. This is because the triple valves on the cars can only operate this way. But when you drive your car you frequently "ease off" the brakes without releasing them completely. This is because as you slow down you need less braking effort to slow down and stop. If you keep your foot hard on the brakes right to the stop it's a bit like hitting a brick wall when you stop! Westinghouse got round this problem in passenger cars by developing a special control valve for each car that allows a graduated release. You can put the brakes on full but as the train slows down you can move the brake handle back toward release (but not all the way) and the brake pipe pressure goes back up but not all the way. In the cars the brakes release a little but are still applied. By the time the train is coming to a stop it is possible to move the brake to release and still stop. Obviously you can only use this feature when the entire train consists of vehicles with these special control valves. None of the brake valves or consists in Auran have this feature.
"Frt" is used for conventional triple valve fitted stock that only has full release not graduated release. If you move the brake handle back a little after making an application nothing will happen. You have to move it all the way back to release and then you get a full release as per normal.
"Out" is used when the loco is in multiple operation and is NOT the lead loco. It simply renders the brake valve inoperative except that moving the handle into the emergency position will still give an emergency brake application.
Here endeth the lesson!
The big red foot thing could either be a dead man's pedal device (you have to keep it depressed with your foot or the loco will stop) or more likely an alternative sanding device. A picture might be helpful here...
Cheers
Nix
