Low-frequency rumble, high-frequency squeak:
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Morse code, reception, transfer
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SOS signal transmission, Morse code
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Low frequency pulsing and humming signal
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Morse code, SOS signal reception
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Electronic signal, energy buildup
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Radio Setup
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Radar, location alert
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Low frequency electronic signal
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High frequency squeak
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Low-frequency rumble, high-frequency squeak
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Interference Broadcasting
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High frequency signal
★★★★★