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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.
Ringback tone characteristics 
A ring-back tone from the UK
A ring-back tone from North America
A European ring-back tone per ETSI standard
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United Kingdom, Ireland and some Commonwealth nations 
In the UK, Republic of Ireland, Australia, New Zealand, and many Commonwealth nations, it is a double ring. 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. In some countries, the pulse is made by mixing a 400 Hz and 450 Hz sine wave.
The tune "Telephone and Rubber Band" by the Penguin Cafe Orchestra was created using a tape loop that merged the UK ringback tone with the UK engaged tone.
North America 
In North America, the standard ringback tone is a repeating 2-second tone with a 4-second pause between. The tone is 440 Hz + 480 Hz.
Europe (except UK and Ireland) 
Most European countries, other than the UK and Ireland, use tones which follow European Telecommunications Standards Institute recommendations. Many of these tones are 425 Hz. Typically the pattern is 1 second of tone followed by 3 to 5 seconds of silence.
Ringback music 
Also known as caller tunes in some parts of the world (like India), ringback music is a service offered by mobile network operators which enables subscribers to set music or even personalized recorded sounds as ringback tones.
Early versions of personalized ringback tone systems have been invented by a couple of inventors, Kang-seok Kim (Korean patent 10-1999-0005344), Mark Gregorek et al. (U.S. 5,321,740) and Neil Sleevi (U.S. patent 4,811,382). The first functional ringback tone replacement system was invented by Karl Seelig et al. (U.S. patents 7,006,608 and 7,227,929). In 2001 Seelig's prototype was described in the Orange County Register and the Economist Magazine kick starting the world wide development of ringback tone replacement.
Ringback advertising 
Advertising over Ringback tones (AdRBT) was introduced using a range of models across several commercial markets in 2008. In America Ring Plus offered the first interactive advertisement platform. In Turkey, 4play Digital Workshop launched 'TonlaKazaan' AdRBT with Turkcell, and Xipto AdRBT launched in the United States with Cincinnati Bell wireless; OnMobile launched an Ad-supported Music RBT program in India with Vodafone. 4Play Digital workshop accumulated several hundred thousand users of their service in the first few months of commercial deployment, and received an innovation award in February 2009 at the Mobile World Congress in Barcelona. AdRBT typically rewards the caller or the called party with discounted Music RBT service, free minutes, cash, or other rewards in return for accepting advertising messages integrated with Music Ringback, or for selecting advertisements instead of music as a personalized advertising ringback.
In May 2011, Adfortel started the first ad-sponsored call service in Austria with Orange, with users hearing a targeted advertisement instead of the regular waiting ring tone.
A Juniper Research report released in January 2011 that predicts that ringback tone advertising will reach $780 million annually by 2015.
Interactive reverse ringback tone 
Interactive reverse ringback tones (IRRBT) are the same as normal RBTs but have interactive functionalities and are targeted to the person who sets the RBT. IRRBTs are heard on the telephone line by the caller who sets the IRRBT while the phone they are calling is ringing.
Unlike the RBT, the IRRBT is generated in the nearest switch and transmitted in-band, so the IRRBT will take precedence if both are configured.
WiderThan, a South Korean wireless services provider, invented this type of ringback tones for cellphone networks. CRBT (Coloring Ring back tones) are pieces of music and audio clips that callers hear instead of normal ringing tone when they dial a specific number. The original service first premiered by South Korean operator SK Telecom in April 2002. Ringback tones were launched in Europe and North America in 2003 and 2004 respectively.
Social network ringback tones provide interactive social network content to subscribers. Mixcess is the first platform (social network) using IRRBTs in the United States. The IRRBT was developed by Ring Plus, Inc. (U.S. Patent No. 7,227,929 invented by Karl Seelig, et al.). The IRRBT can be used to share videos, music and messages from friends.
Ringback patents 
Patents for personalized ringback tone delivery systems were first filed in Korea by Kang-seok Kim (10-1999-0005344) in October 1999 and in the United States by Mark Gregorek et al. (U.S. patent 5,321,740), Neil Sleevi (U.S. patent 4,811,382), and Karl Seelig (U.S. patents 7,006,608 and 7,227,929). Onmobile Global Ltd. India, Method and system for customizing ring-back tone in an inter-operator telecommunication system Nov, 18 2010: US 20100290602. Onmobile Global Ltd. India, Method and system for updating social networking site with ring back tone information Oct, 7 2010: US 201002558
See also 
- Mark Gregorek et al. (U.S. patent 5,321,740) Neil Sleevi (U.S. patent 4,811,382)
Karl Seelig et al. (U.S. patents 7,006,608 and 7,227,929)
- International Telephone Ring-Back Signaling Reference
- Press Information Bureau of India - Ministry of Communications & Information Technology
- Vodafone India Callertunes
- Airtel Hello Tunes
- John Levett (2011-01-18). "Press Release: Ringback Tone Advertising to Hit $780 million annually by 2015 as Consumers Chase Free Airtime, says Juniper Research". Retrieved 2011-11-09.
- Real Whitepaper - Ringback Tones - Virtual Press Office Ringback Tone Solution & Service. 3. RealNetworks, 2007
- David Wisely, IP for 4G. John Wiley & Sons, 2009
- Emanuel Hanser-Strecker, Modern Mobile Technologies and their Impact on Content Providers. GRIN Verlag, 2006