Page 101 - Asterisk™: The Future of Telephony

You will see the parkedcalls context because it is an internal context to
Asterisk, specified in the features.conf file.

Setting Up the Dialplan for Some Test Calls

Now let’s expand upon the test dialplan we started in the previous section, allowing
us to dial back into the softphone after we have configured it and to use a dialplan
application called Echo() that will allow us to test bidirectional audio. We’ll learn more
about dialplans in Chapter 5, so for now, just add the italicized bits to your existing
extensions.conf file. We’ll be making use of this dialplan throughout the chapter, and
expanding on it in certain sections. Once you’ve entered the text into extensions.conf,
reload the dialplan by running dialplan reload from the Asterisk console:
[globals]
[general]

[default]
exten => s,1,Verbose(1|Unrouted call handler)
exten => s,n,Answer()
exten => s,n,Wait(1)
exten => s,n,Playback(tt-weasels)
exten => s,n,Hangup()
[incoming_calls]

[internal]
exten => 500,1,Verbose(1|Echo test application)
exten => 500,n,Echo()
exten => 500,n,Hangup()

[phones]
include => internal

FXO and FXS Channels

The difference between an FXO channel and an FXS channel is simply which end of
the connection provides the dial tone. An FXO port does not generate a dial tone; it
accepts one. A common example is the dial tone provided by your phone company. An
FXS port provides both the dial tone and ringing voltage to alert the station user of an
inbound call. Both interfaces provide bidirectional communication (i.e., communica-
tion that is transmitted and received in both directions simultaneously). §

§ Bidirectional communication is also known as full duplex in some circles. Half duplex means communication
is only traveling in one direction at a time.

Setting Up the Dialplan for Some Test Calls | 73