| 21. | The operations of these elevators are synchronized by a light signal in the car.
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| 22. | Just then, screaming sirens and flashing lights signal the approach of another Washington motorcade.
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| 23. | Italian light signals consist of one to three single lamps.
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| 24. | According to the rules, light signals are used for main line traffic or shunting.
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| 25. | These semaphore signals remained until 1994 when the line was resignalled with colour-light signals.
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| 26. | The triangular color light signal was especially useful in physically restricted and confined areas.
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| 27. | Later they are replaced by red and green traffic-light signals.
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| 28. | A laser transmitted faint light signals to an electronic detector.
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| 29. | The signal box was removed when semaphore signals were replaced by colour light signals c2010.
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| 30. | A new modernization programme began in 1982, still using mainly two aspect colour light signals.
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