Using DNIS to Direct Calls

Tuesday Oct 29th 2002 by Jonathan Eisenzopf
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Dialed Number Identification Service (or DNIS) is a standard that most telephone companies in the United States use to identify the number that was dialed. In this tutorial, we will learn how to use DNIS information to direct callers to sub-menus in VoiceXML applications.

Dialed Number Identification Service (or DNIS) is a standard that most telephone companies in the United States use to identify the number that was dialed. In this tutorial, we will learn how to use DNIS information to direct callers to sub-menus in VoiceXML applications.

DNIS Overview

This information is frequently used in call centers where callers are directed to a particular operator group based on the dialed number. Call centers that answer calls for many different customers might also use the number to display the name of the company that was dialed so that the customer support representative knows how to answer the phone. In IVR and VoiceXML applications, DNIS information can be used as an alias to direct callers to a specific sub-menu rather than having them drill down a menu hierarchy.

Accessing the DNIS number in VoiceXML

VoiceXML includes a number of built-in session variables. One of those is the DNIS number, which is accessible by specifying session.telephone.dnis as the expr attribute of the <value> element. To test this feature, I dragged the corresponding elements into Nuance V-Builder as seen the example below.

The resulting VoiceXML file is listed and numbered below. If you don't have Nuance V-Builder installed, you can create the VoiceXML dialog by copying the text below into a text editor and removing the line numbers.

1  <?xml version="1.0" encoding="Cp1252"?>
2  
3  <!DOCTYPE vxml PUBLIC '-//Nuance/DTD VoiceXML 1.0//EN' 
4  'http://voicexml.nuance.com/dtd/nuancevoicexml-1-2.dtd'>
5  
6  <vxml version="1.0">
7    <meta name="Generator" content="V-Builder 1.2.30" />
8    <form id="form1">
9      <block name="block1">
10        You have dialed
11  <value expr="session.telephone.dnis" class="digits" />. 
12        Goodbye.
13        <exit />
14        <disconnect />
15      </block>
16    </form>
17  </vxml>

Lines 9 through 15 in the example above will say the number that you dialed, exit the application, and disconnect.

Try it now on Voxeo: Call (408) 689-3992

Directing calls based on DNIS

I worked on a proposal for a local government organization recently who wanted to provide access to schedules and allow customers to register for services over the telephone and on the Web. The organization had several facilities that each wanted to have their own phone number, but still be accessible through the same gateway. I recommended that they have the telephone company assign several numbers to the same line so that the DNIS information could be used to determine which facility was being called.

I call this technique "call destination routing." To demonstrate this functionality, I created an application that might be used in a typical corporation that has separate departments and needs separate, but direct phone access into the VoiceXML IVR system. General requests would come through the main number, where callers can select a department; or callers can dial a direct number assigned to each of the departments that directs callers to the corresponding department menu.

To set up this environment, I added a new application on Voxeo and assigned four numbers to it:

  • 408-689-5161 for the Main number
  • 408-689-3989 for Customer Support
  • 408-689-3990 for Sales
  • 408-689-3991 for Accounting

Now that I had the numbers for each department in hand, I created a VoiceXML document that contained one form and four menus. The form starts on line 8 and directs the call to the menu that corresponds with the DNIS number. If a number wasn't matched, it's assumed that the caller dialed the main number, and is sent to the main_menu <menu> from line 17 to line 21. 

So for example, if you dial 408-689-3989, you will hear, "You have reached the customer service department. To connect to another department, press nine". If you were to dial the main number, 408-689-5161, you would hear, "Main menu. For customer service, press one. For sales, press two. For accounting, press three".

View the source code

If you want to try out this application, you can actually call the numbers that are listed above and be directed to the main menu or you will hear a message from the associated departmental menu.

Conclusion

Directing calls based on DNIS numbers can provide many possible options for directing calls. Utilizing DNIS numbers in conjunction with targeted marketing and promotional responses can improve response rates, increase the number of calls that you can answer, and reduce the number of calls that have to go through your regular PBX or office phones. We will continue talking about call routing in the next tutorial where we will discuss ANI or Automatic Number Identification (also known as Caller ID).

About Jonathan Eisenzopf

Jonathan is a member of the Ferrum Group, LLC  which specializes in Voice Web consulting and training. He has also written articles for other online and print publications including WebReference.com and WDVL.com. Feel free to send an email to eisen@ferrumgroup.com regarding questions or comments about the VoiceXML Strategy series, or for more information about training and consulting services.

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