In telephony, a special information tone (SIT) is an in-band international standard signal consisting of three rising tones indicating a call has failed. It usually precedes a recorded announcement describing the problem.
Special information tones - Wikipedia 
Added 10 months ago by Trav Fryer
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Special information tones - Wikipedia 
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In telephony, a special information tone (SIT) is an in-band international standard signal consisting of three rising tones indicating a call has failed. It usually precedes a recorded announcement describing the problem.
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