In some cases, it can use one mobile device to relay power to another, keeping everything fed even if the main power hub is tied up.

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Laura Bush, coming in the choppy wake of Hillary Clinton, sought to avoid the relay circuits of power, and played the role of quiet booster.

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The relay, put online late last year, triggered unexpectedly, causing another device to stop supplying power to part of the building, Entergy New Orleans told city officials Friday.

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