Electronic signal:
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Interference Broadcasting
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Low frequency electronic signal
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High-frequency squeak, Low-frequency rumble
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Reception, transfer, Morse code
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Horrifying throbbing low-frequency rumble
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White noise
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Electronic signal
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Welcome, Morse code
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Pink noise
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Morse code, SOS signal reception
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Morse code, SOS signal transmission
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Radar, location alert
★★★★★