Generally, coupling is carried out between 2 cars of a train, or even 3. But in some cases, you can attach many more (5,6…).
In some trains, to optimise the aerodynamics, the coupling systems are concealed by a hatch which remains closed when the trains are separated.
In the past, loupling between two cars was carried out manually.
Today, the driver operates the coupling or decoupling function directly from the control panel in his cabin.
The cars are connected by an automatic coupler which contains several systems :
to ensure the mechanical connection between the two cars
to ensure continuity between the two cars and notably the brake control
to connect the cars electronically and enable the control of the two cars from a single cabin.
one of the two cars is stationary, while the second approaches the first at a relatively low speed to limit the jolt felt by the passengers at the moment of connection.