how do they cut the wifi connection once I move in or out of the train?

Question

Specifically how do they cut the train’s station wifi’s connectivity once I am in the train and the train’s wifi’s network offers me to connect inside the train?

In: Technology

Answer 1

The train car is a big metal box. A big Faraday cage.

Faraday cages are very good at blocking the radio waves used by wifi.

Put your phone in the microwave (DO NOT TURN THE MICROWAVE ON) and you will find that also blocks the wifi signal.

That’s how the microwave oven keeps the microwave radiation inside.