Mobile phone and tunnelling shield: what they have in common

1. Step 1. Mobile phone — has part — Printed circuit board. All of a phone's parts are soldered onto a printed circuit board.
2. Step 2. Printed circuit board — is part of — Remote control. Inside a remote is a circuit board with buttons and an infrared LED.
3. Step 3. Remote control — has part — LED. An infrared LED.
4. Step 4. LED — is part of — Street light. LEDs.
5. Step 5. Street light — is part of — Tunnel. Lighting.
6. Step 6. Tunnel — uses — Tunnelling shield. Shield tunnelling.

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