6.7. Handy Asterisk
Features
Now that we've gone over some more of the
basics, let's look at a few popular functions that have been
incorporated into Asterisk.
6.7.1. Zapateller( )
Zapateller( ) is a simple Asterisk
application that plays a special information tone at the beginning
of a call, which causes auto-dialers (usually used by
telemarketers) to think the line has been disconnected. Not only
will they hang up, but their systems will flag your number as out
of service, which could help you avoid all kinds of telemarketing
calls. To use this functionality within your dialplan, simply call
the Zapateller( ) application.
We'll also use the optional nocallerid
option so that the tone will be played only when there is no Caller
ID information on the incoming call. For example, you might use
Zapateller( ) in the s extension of your
[incoming] context, like this:
[incomimg]
exten => s,1,Zapateller(nocallerid)
exten => s,2,Playback(enter-ext-of-person)
6.7.2. Call Parking
Another handy feature is called "call
parking
." Call parking allows you to place a call on hold in a "parking
lot," so it can be taken off hold from another extension.
Parameters for call parking (such as the extensions to use, the
number of spaces, and so on) are all controlled within the
features.conf configuration file.
The [general] section of the features.conf file contains four settings
related to call parking :
parkext
-
This is the parking lot extension. Transfer a
call to this extension, and the system will tell you which parking
position the call is in. By default, the parking extension is
700.
parkpos
-
This option defines the number of parking slots.
For example, setting it to 701-720 creates 20 parking
positions, numbered 701 through 720.
context
-
This is the name of the parking context. To be
able to park calls, you must include this context.
parkingtime
-
If set, this option controls how long (in
seconds) a call can stay in the parking lot. If the call isn't
picked up within the specified time, the extension that parked the
call will be called back.
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You must restart Asterisk after editing
features.conf, as the file is read
only on startup. Running the reload command will not cause
the features.conf file to be
read.
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Also note that because the user needs to be able
to transfer the calls to the parking lot extension, you should make
sure you're using the t and/or T options to the
Dial( ) application.
So, let's create a simple dialplan to show off
call parking:
[incoming]
include => parkedcalls
exten=103,1,Dial(SIP/Bob,,tT)
exten=104,1,Dial(SIP/Charlie,,tT)
To illustrate how call parking works, say that
Alice calls into the system and dials extension 103, to reach Bob.
After a while, Bob transfers the call to extension 700, which tells
him that the call from Alice has been parked in position 701. Bob
then dials Charlie at extension 104, and tells him that Alice is at
extension 701. Charlie then dials extension 701, and begins to talk
to Alice. This is a simple and effective way of allowing callers to
be transferred between users.
6.7.3. Conferencing with MeetMe(
)
Last but not least, let's cover setting up an
audio conference bridge with the MeetMe( )
application. This application allows
multiple callers to converse together, as if they were all in the
same physical location. Some of the main features include:
-
The ability to create password-protected
conferences
-
Conference administration (mute conference, lock
conference, kick participants)
-
The option of muting all but one participant
(useful for company announcements, broadcasts, etc.)
-
Static or dynamic conference creation
Let's walk through setting up a basic conference
room. The configuration options for the MeetMe conferencing system
are found in meetme.conf. Inside
the configuration file, you define conference rooms and optional
numeric passwords. (If a password is defined here, it will be
required to enter all conferences using that room.) For our
example, let's set up a conference room at extension 600. First,
we'll set up the conference room in meetme.conf. We'll call it 600, and
we won't assign a password at this time:
[rooms]
conf => 600
Now that the configuration file is complete,
we'll need to restart Asterisk so that it can re-read the
meetme.conf file. Next, we'll add
support for the conference room to our dialplan with the
MeetMe( ) application. MeetMe( ) takes three
arguments: the name of the conference room (as defined in
meetme.conf), a set of options,
and the password the user must enter to join this conference. Let's
set up a simple conference using room 600, the i
option (which announces when people enter and exit the conference),
and a password of 54321:
exten => 600,1,MeetMe(600,i,54321)
That's all there is to it! When callers enter
extension 600, they will be prompted for the password. If they
correctly enter 54321, they will be added to the
conference. See Appendix B for a list of
all the options supported by the MeetMe( )
application.
Another useful application is MeetMeCount(
). As its name suggests, this application counts the number of
users in a particular conference room. It takes up to two
arguments: the conference room in which to count the number of
participants, and optionally a variable name to assign the count
to. If the variable name is not passed as the second argument, the
count is read to the caller:
exten => 601,1,Playback(conf-thereare)
exten => 601,2,MeetMeCount(600)
exten => 601,3,Playback(conf-peopleinconf)
If you pass a variable as the second argument to
MeetMeCount( ), the count is assigned to the variable and
playback of the count is skipped. You might use this to limit the
number of participants, like this:
; limit the conference room to 10 participants
exten => 600,1,MeetMeCount(600,CONFCOUNT)
exten => 600,2,GotoIf($[${CONFCOUNT} <= 10]?3:100)
exten => 600,3,MeetMe(600,i,54321)
exten => 600,100,Playback(conf-full)
Isn't Asterisk fun? |
