Independent Brake operation on Push-Pull Trains

I am a non-railroader curious about operation of the locomotive independent brake when the cab car is controlling. I assume there is an independent brake valve in the cab car (but no J-1 Relay), and that both the actuating line and the independent application and release line are carried through the train from loco to cab car (along with the brake pipe and the main reservoir line. The whole setup is then equivalent to MU operation of several locomotives as far as control of the loco's independent brake is concerned. Am I correct?

at least on MN there is no independent brake on cab cars or controlled by cab car.
its train brake or no brake at all.

I can't see a cab car controlling the *locomotive* independent brake from the cab car ...

The only implementation I'd see making sense would be an independent brake in the cab car itself ...

and unless the design includes that, there won't be one.

Amtrak Capitoliner Cab Cars have a pneumatic parking brake that is something like an independent brake which applies air only to the F end truck.

well I would suggest using it as holding brake, but not as independent unless you want new wheel true machine named after you.

Metra's gallery cars - 8400 series and newer - are equipped with a 30CDW (fully pneumatic, so called "desktop" type) automatic brake valve with a companion parking brake handle included that looks and functions exactly like an independent brake valve - and they do have a J relay valve. The more brake cylinder pressure you require, the further you push it into the service zone. It builds brake cylinder pressure on all 4 axles of the coach, maxing out at 100psi. Obviously with that kind of BC pressure, it requires the engineer not operate it foolishly when it's being used outside of its intended purpose as a parking brake - but there are plenty of situations on the line of road where it is very useful, and I don't just mean throwing it on when you're coming in to a station too hot.

So far as I know, no push pull commuter operation exists in the US where an independent brake valve in a cab car operates the independent/ actuating feature on the locomotive at the other end of the train. The MU connections don't exist on any equipment and even if they did I would be concerned about the reliability of operating it - that's a long way for MR air to travel on demand rather than being constantly pressurized.

Even the Burlington Budds had #30 brake on them in the 1990s, when I worked there. They did have independent brakes on the cab cars. I have been told that that system came about, and the cars were converted concurrently with the replacement of the E9 fleet with the F40. I don't know what they had before. Part of the conversation was a change from cast, to composition shoes.

Moderator's Note: Moved to General Discussion: Locomotives, Rolling Stock, and Equipment.