Low frequency electronic signal:
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Electronic signal
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High frequency squeak
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Horrifying throbbing low-frequency rumble
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Morse code, SOS signal reception
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Low-frequency rumble, high-frequency squeak
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Morse code, SOS signal transmission
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Morse code, transfer, reception
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Energy buildup, Electronic signal
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Radio noise
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Radio Setup
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Brown noise
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Location alert, Radar
★★★★★