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La communication par infiltration dans la terre (TTE, de l'anglais Through-the-earth), ou comme M. Kohler l'appelle, « le Saint-Graal », pourrait se révéler utile dans un système interopérable. Les signaux totalement sans fil à basse fréquence peuvent pénétrer la surface à travers des milliers de pied de roches, mais on ne les utilisait jusqu'à présent que pour de simples messages à sens unique par le biais d'une antenne cadre à très large surface.
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Through-the-earth communication – TTE, or as Kohler calls it, “the holy grail” – could find its place in such an interoperable system. Truly wireless, low-frequency signals can penetrate from surface through thousands of feet of rock, but their uses until recently have been limited to simple one-way messages via a very large surface loop antenna. Several NIOSH-funded alternatives have improved on that: Lockheed Martin’s MagneLink allows two-way communications, as does E-Spectrum’s Rescue Dog. But Kohler would like to see something even better: a TTE system that could catch another system’s signal and send it to surface.
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