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Phone tone, CCITT4 Key 7.
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This is an CCITT4 Key 6 Phone Tone.
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This is an CCITT4 Key 4 Phone Tone.
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Phone tone, CCITT4 Key
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Phone tone, CCITT4 Key
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Phone tone, CCITT4 Key
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Phone tone, CCITT4 Key
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Sharp high pitch glitch randomly modulating
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Telemetry internal ringtone, modem dialing.