Ringing tone

A ringback tone is the audible ringing that is heard on the telephone line by the calling party after dialing and prior to the call being answered at the distant end. The ringback tone is different in various countries depending on the requirements for the ringback specification in those countries. For example, in the NANP (United States, Canada, and others), the standard ringback signal is generated by summing a 440Hz tone with a 480Hz tone and applying these to the telephone line in a 2 second on and 4 second off cadence. The tone combination produces a warbling "ring... ring..." sound, caused by the 40Hz beat between the two. Most other countries use a single tone, as do some PBX and key phone systems.

Nonstandard uses

In recent years, a form of ringback has become popular on a global basis. This form of ringback is referred to as "personalized ringback". With personalized ringback, callers will hear an audio selection applied to the telephone line that has been previously determined by the called party. Audio selections can include music, messages, and special effects. Equipment is installed in the telephone network to enable replacement of the standard ringback tone with a personalized audio selection. The application of the personalized audio selections is accomplished with a subscriber account that can be modified through WWW, WAP, or IVR user interfaces.

Various companies supply personalized ringback equipment for mobile phone and landline telephone companies. The first company to launch a commercial system in the United States was Preferred Voice, Inc. [1]

The use of such nonstandard telephony signals can cause problems with automatic dialing equipment such as faxes a modems, however lines intended to receive such data telephone calls normally have the proper ringback tone.