A ringback tone (or ringing tone) is an audible indication that is heard on the telephone line by the caller while the phone they are calling is being rung. It is normally a repeated tone, designed to assure the calling party that the called party's line is ringing, although the ring-back tone may be out of sync with the ringing signal.
The ringback tone (or "RBT") is in most cases generated in the distant switch and transmitted in-band. A message is also sent over the signaling system (usually SS7). In most public phone networks the tone is not generated in the handset or by the local switch, as customized tones or voice announcements may be generated by the distant switch in place of a ringing signal.
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Famous quotes containing the word tone:
“There was about all the Romans a heroic tone peculiar to ancient life. Their virtues were great and noble, and these virtues made them great and noble. They possessed a natural majesty that was not put on and taken off at pleasure, as was that of certain eastern monarchs when they put on or took off their garments of Tyrian dye. It is hoped that this is not wholly lost from the world, although the sense of earthly vanity inculcated by Christianity may have swallowed it up in humility.”
—Herman Melville (1819–1891)