O'Reilly logo

Understanding Session Border Controllers: Comprehensive Guide to Designing, Deploying, Troubleshooting, and Maintaining Cisco Unified Border Element (CUBE) Solutions by Gonzalo Salgueiro, Kaustubh Inamdar, Steve Holl, Chidambaram Arunachalam, Arunachalam Chidambaram, Kyzer Davis, Felipe Garrido

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Chapter 7

DTMF Interworking

At some point, you have heard a prerecorded prompt requesting some information, perhaps a credit card number or an employee number. After a couple of presses on the keypad, you magically get the information you were looking for or are connected to a human agent. The underlying framework that enables this seamless transfer of information is known as dual-tone multifrequency (DTMF).

With the advent of voice over IP (VoIP), reliable transmission of keypad button presses end to end became somewhat of a problem, as audio codecs were not optimized for carrying DTMF tones without bringing in a degree of distortion. There was need to engineer a new way of reliably transmitting DTMF. This solution aimed to factor in all the ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required