Low frequency pulsing and humming signal:
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High frequency pulsating electronic signal
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SOS signal reception, Morse code
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Geiger counter
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Location alert, Radar
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Radio noise
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Reception, transfer, Morse code
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SOS signal transmission, Morse code
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Welcome, Morse code
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Low-frequency rumble, high-frequency squeak
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Interference Broadcasting
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Radio Setup
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Low frequency electronic signal
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