Reorder tone

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Reorder tone (usually referred to simply as "reorder" or "fast busy") is a dual-frequency tone of 480 Hz and 620 Hz at a cadence of 0.25 seconds on, 0.25 off. It is used to indicate that a person has dialed an invalid code, or that all circuits (trunks) are busy and/or their call is unroutable. The easiest way to hear this tone on a standard NANP landline is to pick up the phone and press # (number sign). A PBX will often also do this for an invalid extension, while an invalid telephone number on the PSTN usually gets the triple special information tone and a recording.