The early US equipment - Westinghouse High Speed / HSC system is described in this document:
https://archive.org/...stsreport00penn
See pp50-53
The system seems to consist of a standard graduated release triple valve that can be electrically operated by use of three electro-magnets for application, emergency and release.
There are no additional reservoirs other than the auxiliary, service and emergency reservoirs used for normal pneumatic braking.
In this system brake pipe pressure would also be reduced during brake applications allowing it to operate with normal air braked cars in the same train.
I believe the Russian system is similar to this except that it allows for EP only service applications without reduction in the BP pressure. (Emergency application is by rapid reduction of pressure.)
I am sure that Weter can find a diagram of the car equipment.
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ECP braking seems to be functionally similar to modern wire controlled EP systems. (In all such sytems there is a single air pipe running the length of the train, in European and Japanese systems this is the Main Reservoir pipe. The US system differs from these in that the single pipe is the conventional air brake pipe and vehicles must be able to operate using conventional pneumatic braking signals.)
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Also with ECP, the brake pipe remains charged during operation. This allows the reservoirs on the cars to continuously charge making it less likely for the braking air supply to be exhausted. Further, since the cars can also send their status to the locomotive at the front, the engineer can monitor the state of the train and know at any given time the braking capabilities available.
https://en.wikipedia...neumatic_brakes
http://www.railway-t...c-brakes-d.html
It is described like this in an Australian document
https://railknowledg...=MjY1OQ==&rCFU=
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Typical AAR ECP brake systems; replace the service and sometimes the emergency portion with a Car Control Device (CCD) and a vent valve. The AAR ECP system uses an onboard battery to emulate conventional air brake operation during electrical power failure. The AAR ECP system supplies compressed air directly into the brake cylinder from the reservoir/s through full flow control valves. Although in both ROA and AAR systems the pneumatic signal for braking is replaced by an electrical signal, brake operation is still performed using conventional reservoirs and brake cylinders.