Call legs and channel variables

Phone calls to and from FreeSWITCH consist of one or more call legs. A one-legged connection might be something like a user dialing into his or her voicemail. A traditional call between two parties is a connection with two call legs. Recall the following diagram from Chapter 3, Test Driving the Example Configuration:

A call between two different telephones consists of an A leg (calling or originating party) and a B leg (receiving party). Each call leg is also known as a channel, as in an audio channel. Each channel has a set of logical attributes that you might call a list of facts about that particular call leg. Each of these attributes is stored in a corresponding channel variable. In the previous chapter, we learned that a registered user has several channel variables defined, and these variables are included in call legs involving that user. To get an idea of just how much information is available for a call, you can call the information extension at...