System information

Dial by Extension
If somebody calls your system and knows the extension she wants to reach, your au-
tomated attendant should have code in place to handle this.
Although Asterisk can handle an overlap between menu choices and
extension numbers (i.e., you can have a menu choice 1 and extensions
from 100–199), it is generally best to avoid this overlap. Otherwise, the
dialplan will always have to wait for the interdigit timeout whenever
somebody presses 1, because it won’t know if they are planning to dial
extension 123. The interdigit timeout is the delay the system will allow
between digits before it assumes the entire number has been input. This
timer ensures callers have enough time to dial a multidigit extension,
but it also causes a delay in the processing of single-digit inputs.
Building Your Auto Attendant
After you have designed your auto attendant, there are three things you need to do to
make it work properly:
• Record prompts.
• Build the dialplan for the menu.
• Direct the incoming channels to the auto attendant context.
We will start by talking about recordings.
Recording Prompts
Recording prompts for a telephone system is a critical task. This is what your callers
will hear when they interact with your system, and the quality and professionalism of
these prompts will reflect on your organization.
Asterisk is very flexible in this regard and can work with many different audio formats.
We have found that, in general, the most useful format to use is WAV. Files saved in
this format can be of many different kinds, but only one type of WAV file will work
with Asterisk: files must be encoded in 16-bit, 8000 Hz, mono format.
Recommended Prompt File Format
The WAV file format we have recommended is useful for system prompts because it is
a format that can easily be converted to any other format that your phones might use
without distortion, and one that almost any computer can play without any special
software. Thus, not only can Asterisk handle the file easily, but it is also easy to work
with it on a PC (which can be useful). Asterisk can handle other file formats as well,
and in some cases these may be more suitable to your needs, but in general we find 16-
336 | Chapter 15: The Automated Attendant