Police radio:
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High-frequency squeak, Low-frequency rumble
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Low frequency pulsing and humming signal
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High frequency signal
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Morse code transmission
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SOS signal reception, Morse code
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Geiger counter
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Police radio
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Pink noise
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Electronic signal, energy buildup
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Transfer, reception, Morse code
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Radio Setup
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Morse code, SOS signal transmission
★★★★★