Morse code, welcome:
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Low frequency pulsing and humming signal
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Low-frequency rumble, high-frequency squeak
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Radar, location alert
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Electronic signal, energy buildup
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SOS signal reception, Morse code
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Low frequency electronic signal
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Reception, Morse code, transfer
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High frequency pulsating electronic signal
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Radio noise
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Electronic signal
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Police radio
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High frequency squeak
★★★★★