[Weter]

I think, in this case, brake controller is exactly that device, which is called "driver's valve", since aside from complex valve itself, which is controlled by handle, which driver operates, it contains other parts, which, for example:
- define application and release rates, due to internal passes diameters
- make automatic feed of BP against leaks on running (MSTS/ORTS Release) and lap with feed positions,
- maintaining BP pressure equal to EQ res pressure,
- make overcharge/quick recharge action,
- eliminate overcharge on running (our Release) position and
- maintaining max system pressure then,
- make emergency quick application, etc.
As you can see, it only controls BP pressure, so as You said - does nothing with BC pressure on consist units. All that is air distributor's work.
So, You are right about that.
Reading that again, we can see complete list of Train Brake Controller's parameter functions.

The primary function of this device, hence - is automatization of BP pressure control in some cases:
- Driver set pressure in EQ res manually, what is quick, then this controller in the bottom part of valve lowers BP pressure for matching with that value automatically.
- Driver puts handle into release (actually called running) position, and working BP pressure then set and maintained, either from discharge or overcharge BP state.
- Driver set handle into emergency position, and controller open very thick vent into thmosphere, bypassing valve in parallel - for acceleration of BP discharge.
- Driver returns handle from apply to lap with feed position, and brake (BP's discharge) step is fixed and maintained against leaks, in distinction of lap position.

And EP is just addition to that valve, two micro-switches sending electric signals into EP control wires along the train (through amplifier)
So, there are three EP states: release, hold and apply. Release is matching with overcharge and "running" positions of valve, Hold - with lap and "lap with feed", and apply matches lap with feed (or slow apply on some old valves) positions. Further, EPapply persists while valve are advanced up to Apply and EMERGENCY positions.

Also, EP can be turned off by external switch - for testing Automatic brakes or in case of EP failure, e.g. Short circuit, or wires breakdown somewhere along the train.

[cesarbl]

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What's this? New system type for inserting into wagon () section?

Yes, it's another variant of EP brakes, which is selected with ORTSEPBrakeControlsBrakePipe( 1 ) (only available on Unstable releases)
This is the UIC EP brake system, where the application and release wires cause local variations of the brake pipe pressure:

Quote

When a pneumatic braking or release command is given by the driver’s brake valve an electric signal is generated as well, venting or supplying on each single vehicle the brake pipe by solenoid valve connected to it.

[Weter]

Quote

application and release wires cause local variations of the brake pipe pressure

Not exactly my case, as there, EP valves, propelled by solenoids are controlling BC charge/discharge, but not affecting BP pressure directly.

Quote

venting or supplying

Furthermore, since in mine case, the system is single-pipe, nowhere to take resupply air on vehicles - BP, still being in "lap with feed" mode is serving as a supply itself.

[Weter]

About TW ratio - its definitely not about TW, strictly speaking. It's ratio between AR and BC volumes, defining which pressure drop in AR will be at the moment, when BC will gain full service pressure (max force) its roughly similar to BP pressure drop, it defines needed BP working (max system in MSTS terms) pressure, however IRL, with EP application, this BC pressure may be exceeded up to almost BP pressure (and there is a risk of wheels stuck ipothen)

[darwins]

I have been trying to trace some history of air brakes and vacuum brakes. EP brakes are a very difficult area. There have been a lot of variations.

Two examples from the 19th century:

1855 - a continuous, automatic brake was invented by Achard in France. It was an electrically operated mechanical brake.

1887 - the only successful brake for long freight trains in the second Burlington brake trials in USA was an electro-pneumatic brake based on the Carpenter two chamber air brake from Germany.
By the 1900s the Westinghouse single chamber air brake had effectively made two-chamber air brakes extinct. The Carpenter brake company later became Knorr Bremse.

The first EP brakes appeared in regular use on electric multiple unit trains in USA before 1910. The most common format seems to have been something like this:
https://i.imgur.com/9CTs0jx.jpg

This would have included systems such as Westinghouse AMRE with R type triple valves and later AMUE with Universal triple valves.
In early examples in USA the braking was EP only with the air brake as a back up. This method of working was standard in UK from introduction in 1929 until the appearance of ECB brakes in the 1970s.
Operation in USA changed to EP and air together for later versions and this was also the UIC standard for EP brakes.

In 1913 the PRR in USA carried out some experiments with an EP braked train of regular passenger cars, hauled by a steam loco with a 6-ET brake valve.
This was a single pipe system, with electrically operated triple valves. Graduated release was always possible when using the EP brake.

https://i.imgur.com/ICyfgb0.jpg

I do not know if this was widely used in USA, but it is similar to the system that Weter is describing. (It also has some interesting similarities to a modern ECP system!)

There were also versions of this used on electric multiple unit trains. Just like the air braked trains of that era, main reservoirs were joined by a main reservoir pipe.
The MRP was not involve in the EP braking. It only joined the main reservoirs. The brakes were worked by electrically operated triple valves.

https://i.imgur.com/IqFUgyt.jpg

An example of this arrangement is the New York Air Brake Co type PS4 electro-pneumatic brake system.

In later years the Main Reservoir Pipe was for both providing air to the brake cylinders and recharging the auxiliary reservoirs.

https://i.imgur.com/ookmmSd.jpg

Westinghouse also added electro-pneumatic braking to the SME brake system to produce the SMEE / HSC braking system.
Like the SME braking system, service braking was carried out using a 'straight' air pipe.
The normal air train pipe, auxiliary reservoirs and triple valves were only present as an emergency feature.
Rather than supplying all of the air for braking from the driver's brake valve, EP valves on each car charged the pipe from the MRP.

https://i.imgur.com/KuPuD3U.jpg

The SMEE system was used on electric multiple unit trains and diesel railcars in USA. It was also widely used in Japan from the 1950s until the 1970s.

Mitsubishi produced the first operational system without a conventional brake pipe in 1968.
This type of brake is also known ECB - Electrically Controlled Brake.
The fail-safe protection is provided by an electric circuit.
ECB systems are now common on high speed trains, diesel multiple units and electric multiple units around the world.

https://i.imgur.com/iQX8utW.jpg

The final diagram shows an ECP - Electronically Controlled Pneumatic brake. This type of braking is now widely used on freight trains in USA.
In normal operation the brake pipe remains full charged with application and release of individual wagon valves under the control of the engineer.

https://i.imgur.com/clGrWog.jpg

[Weter]

Glad to see this new fundamental research.
Will study present diagrams.
***
Great review.
some good ideas, how to show things, but...
No EQ res shown
Extra branch between MR and DV
Did You try with train brake valve to show two parts of it (manually controlled and automatic), in form of TWO squares? (plus EP command module as a black dash beneath) this bottom automatic part of DV is called "equalizing part" here, BTW (as it connected to EqR and sets BP pressure equal to that)
I'd dare to suggest making reservoirs with oval ends with time.
All devices are actually connected to MR pipe, not MR itself - so its a question, should that be so on diagrams, or present way of connection looks more informative, though less prototypic.

It's maybe, little arrows would help in showing the direction of influence (where air is being supplied/where air pressure affects some devices state); when BC's piston&rod are being extended/retracted; where air is being released to atmosphere.
Yellow or orange color, dashed line or lightning sign would show, where EP signal wires are energized.
TBC.

[Weter]

It would be less informative, due to cluttering the diagram, but otherwise, it has sense to be noted in description, that actually, locomotive do have the same full set of equipment (TV/distributor, AR) as other cars - for functioning of brakes, when it's being transferred in "cold" status (as a wagon) within the train.

So, light-blue is highest pressure, blue - high (MR), red - BP working (reduced MR), rose - lowered BP, green - low variable - BC?

Currently, white means both: device currently out of functioning and zero(atmosphere-equal actually) air pressure.
I'd suggest light-gray for out of functioning state then (where pressure isn't still equal to atmosphere)

Maybe, to tilt affected handles on manual controls by 45 degree?
Especially for angle cocks, which are present between couples train units, but being opened.
TBC

[darwins]

Some good ideas - I may post version 2 for editing at some point. I will try to finish version 1 first though!
Trying to keep as simple as possible. So just showing presence or absence of most important devices in use = those we may need to model in a simulator.
Blue - Main Reservoir Pressure (and or main reservoir pipe)Green - Straight Air Pipe - or air direct from main reservoir at reduced pressureRed - Automatic Air Brake PipePink - Reduced Pressure in Automatic Air BrakeWhite - Atmospheric Pressure

[Weter]

1. Didn't know, it is still WIP.
2. It may be better - to draw continuation with usage of good ideas from the start - so less to re-draw later.
3. You are absolutely right - as less of extra elements as possible - so easier to understand.

The only moment: everything should be explained - for everyone (not You as an author) would see (but not guess) its right purpose/state/function(or functional mutual connection)

Blue - indeed they are certainly equal, but note, that You've mentioned a special (second?) pipe, what is used for feeding train brakes, but is under constant, reduced, relative to MR, pressure. Or, maybe, it has nothing common with EP systems, to which present review is dedicated.

In our code scheme, by the way, Green is BC - connected pipe(s), and ivory - independent brake (straight-action) pipe.

[darwins]

The first mention I can find of an air brake, is one on individual cars, 1848 - Lister air brake, UK, non-automatic, not continuous

The first practical air brakes were direct air brakes.
1860 - Wenger, France, continuous non-automatic air brake
1862 - McInnes air brake, UK, used on Caledonian Railway
1869 - Westinghouse straight (non-automatic) air brake

https://i.imgur.com/pX6tIV4.jpg

The first automatic air brake was produced by Westinghouse in 1873.
This was a single chamber brake using a triple valve.

https://i.imgur.com/xi1PWRF.jpg

1875 - Perkins, USA, triple valve for automatic air brake
1875 - Westinghouse improved triple valve

The alternative to this was a two-chamber air brake. This system did not require a triple valve, but was generally slower in operation.
(The automatic vacuum brake, which I will post later uses a two-chamber system.)

https://i.imgur.com/bUc1qlX.jpg

1878 - Prince, USA, two chamber automatic air brake
1878 - Clark, UK, two chamber automatic air brake with balancing valve
1883 - Carpenter, Germany, two chamber automatic air brake used for passenger trains on Prussian State Railways (also Bergen-Vossewangen in Norway,? in Spain and ? in Russia)
1883 - Wenger, France, continuous automatic air brake, additional valves on each car made the Wenger brake faster acting than other two-chamber brakes.

In the meantime development of the single chamber air brake continued

1879 - 'Running position' to maintain brake pipe pressure added to Westinghouse driver's brake valve
1879 - Independent brake for driving wheels added to Westinghouse system (entirely separate and not integrated with automatic brake!)
1879 - Westinghouse, standard plain triple valve

The main problems with the Westinghouse brake were direct rather than graduated release and the time taken to recharge auxiliary reservoirs.
This made the brake unsuitable for routes with long steep gradients. Many of these opted for the automatic vacuum brake.
In 1881 Henry produced a combined direct and automatic air brake for the PLM in France.

https://i.imgur.com/pIFw7GC.jpg

In addition to the PLM the Westinghouse-Henry double brake was widely used on narrow gauge lines in Hungary.

1885 - Cosgrove USA, combination independent and automatic brake valve for emergency use
1886 - Equalizing valve introduced by Westinghouse

https://i.imgur.com/AQIoKBg.jpg

Some railway companies, such as the LBSCR in UK, continued to use air brakes without equalising reservoirs for many years after this.

The retaining valve, for use descending steep gradients was introduced around 1893.

The first integrated independent locomotive air brakes appeared in the 1890s/1900s using a double check valve system (Westinghouse A1).

https://i.imgur.com/AQIoKBg.jpg

Later systems, from 1905 onwards, used a kind of proportional valve. (Distributing valve in Westinghouse 5-ET and 6-ET).

https://i.imgur.com/OybyAAM.jpg

Some railways, used a steam brake as the independent brake.

https://i.imgur.com/48Z8yCo.jpg

Brakes for electric trains began to include a Main Reservoir Pipe that joined together all of the reservoirs on all of the motor cars.

https://i.imgur.com/nzTPc9z.jpg

Another development around this time was the Westinghouse SME brake system.
Like the Westinghouse Henry double brake this combined a straight air brake with an automatic air brake.
The automatic air brake was for emergency use only.
This system was mostly used in trams, but also in some short electric trains.

https://i.imgur.com/XVarC2F.jpg

This was later developed into the SMEE electro-pneumatic brake.

Emergency reservoirs (or supplementary reservoirs) began to be added to air brake systems in North America.

https://i.imgur.com/UCoCDQC.jpg

This was followed by the division of the auxiliary reservoir into a separate auxiliary reservoir and service reservoir. (UC triple valve - 1911)

https://i.imgur.com/OuAcQmR.jpg

The first modern distributor was introduced by Hildebrand-Knorr in 1932.

Later in the 20th century, (possibly in 1950s - I do yet have a date) the modern twin pipe air brake system began to be used.
This was probably derived from the use of a reservoir pipe on multiple unit trains using air or EP brakes.

Twin pipe system for multiple unit trains.

https://i.imgur.com/00QPkcI.jpg

Twin pipe system for locomotive hauled trains.

https://i.imgur.com/SPthdxx.jpg