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Implementing CRBT using ISDN PRI links

Caller Ring Back Tone or CRBT has become major revenue earner for both teleom companies as well as value added service providers. Not to mention, music companies. Though, I personally prefer the “good old” ring back tone to the latest music number, but many people have been using it on their cell phone, or even land line numbers.

Occasionally, I keep getting mails about how CRBT can be implemented, recently one guy mailed me specifically, “could we implement CRBT locally in our PABX installed in our office ?”, It got me thinking, and I thought I would share my thinking here. Yes, anyone can implement CRBT or caller ring back tone ( Color Ring Back Tone is also used by some, specifically in Dialogic Application Notes) in their PABX system as long as it has digital interface for CTI boards. Technically, that is. Be careful with music copyright though!

But, in a way, CRBT was always present in PBX system in the form of HOLD music during transferring a call, call parking, call on hold ( in a limited way of course)! The same hold music was converted to CRBT which became very successful in terms of hype and revenue.

I have always maintained that CRBT is nothing but an IVR application which generates lot of money ( for Telecom companies) and which has brought IVR to masses! So, it order to implement CRBT, all you need is IVR applicaion with database integration!

Here is how one can implement CRBT on a ISDN PRI in a on premise PABX :-

  • Every incoming call is send to IVR application by PBX which is connected PBX using ISDN link.
  • IVR applications receives the incoming call on say channel A, retrieves “dialed number” information from the incoming call.
  • IVR then checks the database if the dialed number has subscribed to CRBT and also a particular music.
  • IVR now dials out the “dialed number” using separate and available channel ( say channel B) of the ISDN Link and checks if it is ringing. If yes, then it plays the particular music to the incoming call ( CRBT of dialed number for the caller). If not, it is busy, it will play busy tone or directly bridge both the channels, ie incoming and outgoing channels A and B.
  • As soon as channel B detects call pick up by the “dialed number”, it will bridge both channel A and B.
  • When any one of the parties disconnects, change back to original!

This scheme may not be the optimal solution for implementing CRBT as it uses two channels known as trombone, but this works! Did I mention, you must use Digital CTI board which supports call bridging feature ? Almost all Dialogic digital boards or equivalent from other manufacturers have this facility.

So, if someone is thinking of implementing CRBT for one’s office, you may see all people dialing each other, listening to music!

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{ 3 comments… add one }
  • Nitin June 30, 2012, 10:09 pm

    Is it Possible to Play Some CRBT Tone to the Outside Caller without answering the Call on the Tata, Reliance, Airtel, Aircel PRI Lines in India.

  • randeep December 10, 2012, 12:25 am

    hi !
    i need to jf one needs to be CRBT VAS content provider what h/w and s/w infrastructure should one have apart from content and rights to content.

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