busy signal

A busy signal (or busy tone or engaged tone) in telephony is an audible or visual signal to the calling party that indicates failure to complete the requested connection of that particular telephone call.

There are several types of signals known as busy signals:

• a reorder tone, (sometimes called a fast busy signal), indicates that no transmission path to the called number is available.
• an otherwise unspecified busy signal indicates that the called number is occupied or otherwise unavailable
• this tone sometimes occurs at the end of a call to indicate the other party has hung up. See disconnect supervision.

Many different countries have different signalling tones that act as "busy signals".

	Example of a North American busy signal Listen to a busy signal from North America. Example of an old North American busy signal Listen to a busy signal from North America used prior to the 1980's.
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References

• Federal Standard 1037C
• MIL-STD-188

External links

• World PSTN Tone Database - Busy tones