●call-waiting ringback tone — A ringback tone with a lower-pitched signal at the end; indicates that the extension called is busy, but the called party has been given a call-waiting tone.
●confirmation tone — 3 short bursts of tone; indicates that a feature activation or cancellation has been accepted.
●coverage tone — 1 long burst of tone; indicates that your call will be sent to another extension to be answered by a covering user.
●dial tone — A continuous tone; indicates that dialing can begin.
●intercept/time-out tone — An alternating high and low tone; indicates a dialing error, a denial of the requested service, or a failure to dial within a preset interval (usually 10 seconds) after lifting the handset or dialing the previous digit.
●recall dial tone — 3 short bursts of tone followed by a steady dial tone; indicates that the feature request has been accepted and dialing can begin.
●reorder tone — A fast-busy tone repeated 120 times a minute; indicates that all trunks are busy.
●ringback tone — A low-pitched tone repeated 15 times a minute; indicates that the number dialed is being rung.