RCO locomotive question

[David Collins]

https://youtube.com/shorts/2g4llUoQl5I?feature=shared

I found this YouTube short of two guys testing the RCO equipment on a newly RCO equipped BNSF (former Santa Fe) Dash 9…and yes, you read that right, BNSF is making some of the warbonnet Dash 9’s into Remote Control units.

Is there any chance someone can enlighten me as to:

A. Why they left the brakes on emergency and full independent, do crews set that before hand and then the RCO system takes over control over the brakes?

B. The guy says “control voltage is 31”, then says 40 and 42. What is that? Something to do with the amperage on the locomotive?

[amessmann]

A. It could be a reason of safety like you said, but I wonder if they needed an engine load for the test. It sounded like the engine was pushing pretty hard against them.

B. A control voltage could be any number of things, as the name implies, it is a voltage on a wire that controls something. It is an analogue signal, as opposed to a digital signal like a PWM signal (square wave who's "high" time (width) is modulated). I imagine in this case, it could be the electricity that builds the generator field, or controlling the circuits that run that. It could just be the signal controlling the throttle, higher voltage means higher throttle position for example. It could be a signal going to the ammeter. "Control voltage" is much to broad a term to pinpoint exactly what it could be, I'll bet there are numerous different voltages on hundreds of control wires inside a given locomotive, especially one from the 1980's or newer.

I'll be clear that I am absolutely speculating here, as the electronics of a locomotive far exceed my technical knowledge. I would pay good money to know the in-depth details of how these things operate, the blend of electronics and machinery is what draws me track side anyway.

[BnOEngr]

The brake console is set up for "trail". The automatic is in Handle Off position and the independent is cut-out. The remote system has its own brake control valves.
Not sure what he is talking about on "control voltage", unless he is reading a meter on the back wall. The meter on the right is the ammeter, doesn't show voltage. Maybe he mispoke.

[pudgy]

Looks and sounds like they are troubleshooting a problem on the engine. They are putting it in speed step "Hump", which is limited to 1 mph. When they say brakes are applied, believe they have the train brake applied on the cars to increase the loading of the engine. Counting out numbers is how many amps the loco is loading on the amp meter, an indication of how properly it's working.