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I keep getting various questions about CRBT ( Caller Ringback Tone) and IVRS, their relation. My answer is CRBT is essentially an application that uses IVRS and smart call routing.
This CRBT is marketed by different names by different Mobile Operators! The list might be interesting to publish! Most commonly used in India are, Hello Tunes, Caller Tunes, Dialer Tune etc.

What is CRBT?
When person A calls person B, if person B is available, then person A hears a ringback tone! Now CRBT replaces that ringback tone with a selectable music. So, now, a person A dials person B, person A gets to hear a music, person B has selected as his CRBT Tone. Person B has also option for playing a particular music according to caller ID. For example I can set music “Welcome to the Hotel California” when my friend calls me while I can record a message, “Testing IVR Application” which will be played when ever my boss calls me.

CRBT can be implemented various ways! The easiest way is using SS7 call routing and IVRS. ( This is not a technical guide to start a CRBT Service, but just logical explanation. For technical solution, contact me separately or any other CRBT Solution provider.)

1. Switch receives a call from Subscriber A to Subscriber B.

2. Switch routes the call to IN ( Intelligent Network) System. IN System will check if subscriber B is available, if yes, it checks if Subscriber B is a CRBT Subscriber. If no, it sends back to the call to connect the call normally. If yes, it asks switch to dial out Subscriber B, while it transfers the call to CRBT Server, which is nothing but IVRS Server. As soon as IVR receives the call, it plays back the pre-programmed music as per caller id or the Subscriber B.


3. IN System keeps monitoring the switch dialing out to Subscriber B. As soon as Subscriber B receives the call, or disconnects it, IN system disconnects from CRBT Server, asks switch to connect subscriber A and Subscriber B.

Quite simple, eh ? Not actually! A CRBT server needs quite a bit hardware, many big Teleocm jargon, like MTP, ISUP, SCP, SSP, SS7 Link, MAP apart from big database of music, along with copyrights!

If you are jumping the CRBT business after seeing those advertisement and news on news papers, you may have to do a rethinking!

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{ 24 comments… add one }
  • Joel April 15, 2009, 2:06 pm

    Thanks for the information about the IN based CRBT. Would you know how the RLT is being implemented for CRBT. We don’t have IN yet and we wanted to know if RLT or Release Line Trunk is common to all switches and how it is being configured.

  • Uttam Pegu April 15, 2009, 5:30 pm

    Hi Joel,
    Thank you for dropping by.

    Yes, CRBT or PRBT can be implemented without IN too. But people prefer IN for obvious reason.

    In an NON-IN situation, normally all calls are routed to CRBT Server. CRBT Server does the call answering, as well as making out going calls to the called party by the caller! Most of the time, CRBT Server server has to use two links from Switch, one for receiving calls and other to make outgoing calls and then connect the two calls use RLT!

    Having said, I am not exactly switch expert, I work more on IVR Application part. But above description should give you an idea how CRBT can be configured without IN.

  • Avinkr April 17, 2009, 11:10 pm

    Can you help in identifying Hw for CRBT and helping us out in configuring Demo.

  • Uttam Pegu April 18, 2009, 11:52 am

    Hi Avinkr,
    Yes, I can help you in identifying Hardware as well as preparing a demo.


    Uttam Pegu

  • Avinkr April 20, 2009, 2:24 pm

    MY Contact details are avinkr@rediffmail.com why dont we directly start communicating on mail and phone, let me know your email id as well,


  • Sameer Jadhav October 21, 2009, 11:26 am

    Hello, I am Sameer Jadhav from MUMBAI, I am working for Trupti Movies as a Market Research Manager, Recently Our company had published New Songs for MAHARASHTRA NAVNIRMAN SENA (MNS) Which is leaded by Shri Rajsaheb Thackray, Reason for sending this letter to you is that, we need to PUBLISH are songs in the form of Callertunes, We have already approached AIRTEL and MTNL and we have got a good response, We have published our advertisement in Newspaper also and our songs are very much demanding, We would like to approach you also for this concern, PEOPLE OF MAHARASHTRA WILL LOVE TO KEEP THIS RINGTONE AND KEEP MARATHI FAME (ASMITA) ALIVE IN THIER HEART, Please revert back to us as soon as possible, Contact number: 9930567165 : Sameer Jadhav.

  • Uttam Pegu October 21, 2009, 11:44 am

    Dear Mr. Sameer,
    Thank you for writing to us. I would recommend you to ask the mobile operators ( Airtel, MTNL, Vodafone etc.) for the CRBT vendor in their respective network. I think, IMI Mobile, Hyderabad, OnMobile, Bengaluroo, Spice Digital ( Previously known as Cellbrum) offers CRBT services in Mumbai and Maharashtra. They would be able to add the songs in their caller tunes.
    We provide only technical services like establishing a CRBT service for a telecom operator and do not run any CRBT services for any operator.

    Thank you and best regards

  • Mukesh November 13, 2009, 11:55 am

    Hi ,

    I am mukesh. I am a student completed my BE(Electronics and Telecommunication ) and want to learn about the CRBT in technical(implementation) perspective. So can help me to start with the CRBT … by providing some doc …

  • Uttam Pegu November 14, 2009, 11:26 pm

    Hi Mukesh,
    You should visit http://www.dialogic.com. They have some documents on CRBT.
    They also have document on how to implement CRBT. But CRBT as an application is IVR software only.
    The calls are routed smartly to play music in place of traditional RBT.

  • Anil June 11, 2010, 2:38 pm

    Explain CRBT call flow

  • Uttam Pegu June 11, 2010, 11:03 pm

    Hi Anil,
    CRBT ‘call flow’ majorly depends on how it is configured at operator end! It can also be implemented using a normal PRI link, you may refer to this post


    Hope this helps.

  • rajeev December 28, 2010, 5:38 pm

    moving forward, can you provide information ion Reverse CRBT and types of CRBT ?

  • Uttam Pegu December 30, 2010, 11:46 am

    Hi Rajeev,
    You may want to check this about Reverse RBT : http://www.ivrsworld.com/general/next-generation-crbt-listen-song-of-your-choice/

    • Ashwin August 4, 2013, 9:01 pm

      Hi Uttam,
      Thanks for your information, but can you give me a brief idea about the call flow modifications implemented at VMSC in order to facilitate Reverse RBT.

  • manisha khandekar February 15, 2011, 2:04 pm

    Hi ,
    I used to get crbt list earlier with lots of songs specially marathi i m looking for .But now List of songs looks very small.
    I am looking Shankar Mahadevan’s …Gananayakay Ganadhishay….song which i m not able to get code no for.
    can u please guide me
    Thank you

  • Mohamed Mohsen March 7, 2012, 9:47 am

    after implementing CRBT in our network with ericsson as a vendor, we noticed an increase in the Call Drops which can’t be justified with any of the optimization team, i hope you can help me to find a reason for this. thanks a lot in advance.

    Mohamed Mohsen

  • Tele-Columnist! March 21, 2012, 12:02 pm

    Hi Mohamed,
    The Probable reasons for the issue that you are facing due to these probable reasons:-

    1. Signaling link Congestion with CRBT is making the call silent in place of Caller Tune for the subscribers who have opted for the CRBT service.
    2. The CIC or E1 mismatch which can makes inappropriate or mixing your callers with strange caller tunes which the B party has not opted for.
    This issue is in peak hours of traffic or its is their all day around.

    Hi Uttam,
    Cheers for this informative post.


  • rameshrai August 31, 2012, 8:40 pm


    I have a animation of signal flow in a crbt in IN system, easy to understand

  • Aaditya January 16, 2017, 10:49 am


    I’m working in glamour industry and having my own Production House. I have plenty of Music Tracks. So want to create a CRBT & Ringtones content of same but I’m getting any CRBT vendor in Mumbai. I have communicated with Spice Digital, they said they don’t provide such service.
    So I would be great full if you can provide me information about CRBT Vendors for mobile operators.
    Thank you!

  • Chandru December 16, 2017, 4:47 pm

    Hi it’s Chandru from Bangalore I am music director I need to start CRBT service to my upcoming movie songs ..any help how to do it.. in all telecom .. I to do this business..?

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