A Ring-back Tone
(RBT), or Audible Ringing Tone
or Ring-back Signal
, 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 receiving end. This tone assures the calling party that a ringing signal
is being sent on the called party's line, although the ring-back tone may be out of sync with the ringing signal.
Ring-back tone characteristics
The ring-back tone
is different in various countries depending on the requirements for the ring-back specification in those countries. The ring-back signal may be generated by the called-party servicing switch(S-MSC) or by the calling-party switch (O-MSC), but it is not generated by the called telephone instrument. It is generally started and stopped at the same rate as the ringing signal itself but perhaps out of phase.
United Kingdom and the Commonwealth
In the UK
and many other Commonwealth
countries, it is a signature double beep. For most countries, it consists of a 0.4-second pulse, a 0.2-second pause, a 0.4-second pulse, and a 2-second pause. The pulse is made by mixing a 400 Hz and 450 Hz sine wave.
This tone has been made famous by being included at the end of Pink Floyd's "Another Brick in the Wall (Part 2)" and "Young Lust". It is also used in Spacehog's song "In the meantime", as well as The Penguin Cafe Orchestra's "Telephone and Rubber Band".
North American Numbering Plan
In the NANP
, and others), the standard Audible Ring
or ring-back signal is generated by summing a 440 Hz tone with a 480 Hz 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.
Rest of the world
Most other countries use a single tone, as do some PBX
and key phone systems
In some countries, for example India, ringback tone is referred to as dialer tone.
Personalized ring-back tone
In recent years "personalized" ring-back tones have become globally popular. With this feature, 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, greetings and special effects like mixing. Equipment is installed in the telephone network to enable replacement of the standard ring-back tone with a personalized audio selection. This ensures that the handset equipment is not burdened with media storage and playback .The application of the personalized audio selections is accomplished with a subscriber account
that can be modified through WWW
, USSD or Voice User Interfaces
, as well as by customer care personnel.
The first personalized ring-back tone service called Color Ring Back Tone (CRBT) was invented by a South Korean company, Witcom in May 2001 and started service with SK Telecom in South Korea from April 2002. Witcom also developed CRBT IP server for mass service as well. In March 2004, Vodafone D2 was the first European operator to launch the Ringback Tone service. Vodafone used the European Computer Telecoms (ECT) solution.
Today various companies supply personalized ring-back equipment for mobile phone and landline telephone companies. Most mobile operators offer RBT services to their customers. The first company to launch a commercial system in the United States was Preferred Voice, Inc. Most global communication companies now have ringback equipment provided by VAS vendors like Livewire Mobile,RealNetworks,FFCL, Huawei,Alcatel-Lucent, Comverse Technology, Ericsson, Nortel,Eluon, Wind Mobile OnMobile and SixDee.
The majority of mobile operators provide RBT services to their customers. Some operators use a multi-country system, with one RBT system providing content and subscriber services to each country market. The most notable is Vodafone which has 18 local markets. The rollout was done with LogicaCMG doing most of the system integration, using the MyCaller system from Livewire Mobile(was formerly NMS communications) as an RBT solution, although some Vodafone operators are using different platforms, such as Comverse's Fun Dial platform used by Vodafone Italy.
The use of such nonstandard telephony signals can cause problems with automatic dialing equipment such as faxes and modems, however lines intended to receive such data telephone calls normally have the proper ring-back tone. In addition, a caller may define specific users to whom the personalized content will be played. Other callers will hear the "traditional" ring-back tone.