The pattern of damage was similar to the pattern of big-storm frequency uncovered by Dr Elsner.

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Both sending and receiving stations would, however, need some mechanism to encode and control the frequency-hopping pattern.

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It could change the frequency of the Pacific pattern known as El Nino, a cycle of peculiar weather that affects ocean currents and rainfall across the planet.

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Extrapolating from Dr Freund's laboratory experiments, the strain in a real-life geological fault such as the San Andreas could, as it shifted, generate hundreds of thousands of amperes per cubic kilometre in a fluctuating pattern that would cause very low frequency radio waves to be emitted, thus disrupting the ionosphere.

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Moreover, since the resulting interference pattern also depends on the waves' frequency, the same array can concentrate SAWs in different ways at different frequencies, working the liquid sample in different ways.

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Then, they're able to make selections by focusing on an icon that flashes at a distinct frequency from others, which the system recognizes as a unique electrical pattern.

ENGADGET

The trick is to tune the crystal, by modifying the details of pattern, so that as much of the emitted energy as possible is at the frequency most efficiently captured by indium gallium arsenide.

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