Ringback is an intermittent audio tone that a caller in a telephone system hears after dialing a number, when the distant end of the circuit is receiving a ringing signal. It can be generated by the servicing switch of either the called party or the calling party. It is not generated by the called instrument. Ringback is also known as the audible, the audible ringing tone, the ringback tone, and the ringtone .
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The presence of ringback does not necessarily mean a distant device has been actuated. For example, if the circuit and the distant phone line are in proper working order but no phone set or other device is connected at the called-party end, the calling party will hear ringback anyway. The absence of ringback generally indicates that the distant end of the circuit has not been contacted.
The term ringback is sometimes used in reference to a ringing signal that a caller receives when a delayed automatic-calling system places a call to a distant device.