Asterisk: The Definitive Guide, 5th Edition

Chapter 16. Introduction to Interactive Voice Response

One day Alice came to a fork in the road and saw a Cheshire cat in a tree. “Which road do I take?” she asked.

“Where do you want to go?” was his response.

“I don’t know,” Alice answered.

“Then,” said the cat, “it doesn’t matter.”

Lewis Carroll

The term Interactive Voice Response (IVR) is often misused to refer to an automated voice attendant, but the two are very different things. The purpose of an IVR system is to take input from a caller, perform an action based on that input (commonly, looking up data in an external system such as a database), and speak a result to the caller. The purpose of an automated attendant (which we covered in Chapter 14) is to route calls. Originally, an IVR didn’t even need to be a telephone system. Anything that took input from a human and spoke back a result fell with the realm of an IVR. Traditionally, IVR systems have been complex, expensive, and annoying to implement. Asterisk changes all that.

Components of an IVR

The most basic elements of an IVR are quite similar to those of an automated attendant, though the goal is different. We need at least one prompt to tell the caller what the IVR expects, a method of receiving input from the caller, logic to verify that the caller’s response is valid input, logic to determine what the next step of the IVR should be, and finally, a storage mechanism for the responses, if applicable. We might think of an IVR as a decision tree, although it need not have any ...