RAIL - Many EMU's are provided with automatic couplers, usually at the ends of the unit. The coupler provides for all electrical, mechanical and pneumatic connections and is usually remotely operated from the driver's cab, or at least, inside the car. In the case of the MR pipe connection, a valve will open to provide the connection to the next unit once the cars are confirmed as coupled.
Often, automatic couplers are operated by a compressed air supply. This is used to provide power to engage and disengage the mechanical coupling and to open and close the connecting valves and contacts. (099)