Ballast tank and payment card: what they have in common

1. Step 1. Ballast tank — uses — Compressed air. The tanks are blown with compressed air.
2. Step 2. Compressed air — is used in — Air brake. The brake is controlled by air pressure in the train pipe.
3. Step 3. Air brake — evolved into — Anti-lock braking system (ABS). Anti-skid systems first appeared in aviation and on railways.
4. Step 4. Anti-lock braking system (ABS) — has part — Hall sensor. Sensors measure the wheel speed.
5. Step 5. Hall sensor — uses — Magnetism. It responds to a magnetic field.
6. Step 6. Magnetism — is used in — Payment card. A magnetic stripe.

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