Combat vehicle and railway semaphore: what they have in common

1. Step 1. Combat vehicle — includes — Armoured car. A combat vehicle.
2. Step 2. Armoured car — evolved from — Car. A car with armour.
3. Step 3. Car — has part — Turn signal. Turn signals.
4. Step 4. Turn signal — uses — Relay. A flasher relay.
5. Step 5. Relay — is part of — Traffic light. Relay controllers.
6. Step 6. Traffic light — evolved from — Railway semaphore. The first traffic light was a railway-style semaphore.

Open Evothings