AT&T ISDN 7506, ISDN 7507, ISDN 7505 manual

●call waiting tone — One, two, or three beeps of high-pitched tone, not repeated; indicates an incoming call is waiting to be answered. Number of beeps designates the source: 1 for an internal call, 2 for an outside or attendant call, 3 for a priority call.

●confirmation tone — Three short bursts of tone; indicates a feature activation or cancellation has been accepted.

●coverage tone — One short burst of tone; indicates your call will be sent to another extension to be answered by a covering user.

●dial tone — A continuous tone; indicates dialing can begin.

●intercept/time-out tone — An alternating high and low tone; indicates a dialing error, a denial of the service requested, or a failure to dial within a preset interval (usually 10 seconds) after lifting the handset or dialing the previous digit.

●recall dial tone — Three short bursts of tone followed by a steady dial tone; indicates the feature request has been accepted and dialing can begin.

●reorder tone — A fast busy tone repeated 120 times a minute; indicates all trunks are busy.

●ringback tone — A low-pitched tone repeated 15 times a minute; indicates the number dialed is being rung.

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