Signal tower definitions

Signal tower

1) Director of railway trains
Found on https://www.crosswordclues.com/clue/signal-tower

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signal tower

(from the article `Great Wall of China`) Signal towers were also called beacons, beacon terraces, smoke mounds, mounds, or kiosks. They were used to send military communications: beacon ...
Found on http://www.britannica.com/eb/a-z/s/93

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