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use a telephone and the dialplan to create and manage your own
system recordings (or import .wav files).
To use Playback(), specify a filename as the argument. For example, Playback(file
name) would play a sound file called filename.wav, assuming it was located in the
default sounds directory. Note that you can include the full path to a file if you want,
like this:
Playback(/home/john/sounds/filename)
The previous example would play filename.wav from the /home/john/sounds direc‐
tory. This can be problematic, however, due to potential file permissions problems. If
you’re planning on having a lot of custom sounds on your system, you’ll likely want a
dedicated directory for them, and you’ll need to test to ensure Asterisk can find and
play the files.
You can also use relative paths from the Asterisk sounds directory, as follows:
Playback(custom/filename)
This example would play filename.wav from the custom subdirectory of the default
sounds directory (probably /var/lib/asterisk/sounds/en/custom/filename.wav). If the
specified directory contains more than one file with that filename but with different
file extensions, Asterisk automatically plays the best file.6
The Hangup() application does exactly as its name implies: it hangs up the active
channel. You should use this application at the end of a context when you want to end
the current call, to ensure that callers don’t continue on in the dialplan in a way you
might not have anticipated. The Hangup() application does not require any
6 Asterisk selects the best file based on translation cost—that is, it selects the file that is the least CPU-intensive
to convert to its native audio format. When you start Asterisk, it calculates the translation costs between the
different audio formats (they often vary from system to system). You can see these translation costs by typing
core show translation at the Asterisk CLI. The numbers shown represent how many microseconds it takes
Asterisk to transcode one second of audio.
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Chapter 6: Dialplan Basics
arguments, but you can pass an ISDN cause code if you want, such as Hangup(16),
and it will be translated into a comparable SIP message and sent to the far end.
As we work through the book, we will be introducing you to many more Asterisk
applications, but that’s enough theory for now; let’s write some dialplan!
A Basic Dialplan Prototype
To reiterate, then, the form of all dialplans is built from those four concepts: Context,
Extension, Priority, and Application (Figure 6-3).
Figure 6-3. Dialplan prototype
A Simple Dialplan
OK, enough theory. Open up the file /etc/asterisk/extensions.conf in your favorite edi‐
tor, and let’s take a look at your first dialplan (which was created in Chapter 5). We’re
going to add to that.
Hello World
As is typical in many technology books (especially computer programming books),
our first example is called “Hello World.”
In the first priority of our extension, we answer the call. In the second, we play a
sound file named hello-world, and in the third we hang up the call. The code we are
interested in for this example looks like this:
exten => 200,1,Answer()
same => n,Playback(hello-world)
same => n,Hangup()
If you followed along in Chapter 5, you’ll already have a channel or two configured,
as well as the sample dialplan that contains this code. If not, what you need is an
extensions.conf file in your /etc/asterisk directory that contains the following code:
[general]
[globals]
[sets]
A Simple Dialplan
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exten => 100,1,Dial(PJSIP/0000f30A0A01) ; Replace 0000f30A0A01 with your device name
exten => 101,1,Dial(PJSIP/SOFTPHONE_A)
exten => 102,1,Dial(PJSIP/0000f30B0B02)
exten => 103,1,Dial(PJSIP/SOFTPHONE_B)
exten => 200,1,Answer()
same => n,Playback(hello-world)
same => n,Hangup()
If you don’t have any channels configured, now is the time to do so.
There is real satisfaction that comes from passing your first call