[Asterisk-doc] docs/volume-one vm1chp4-channelconfig.xml,1.8,1.9
jimvanm
cvs at sohoskyway.net
Sat Oct 2 13:17:00 CDT 2004
Comments:
Update of /cvsroot/asterisk/docs/volume-one
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv24218/volume-one
Modified Files:
vm1chp4-channelconfig.xml
Log Message:
Reworked the decriptions of FXO vs FXS. Added some verbiage. Changed some stuff around. Edited fearlessly.
Index: vm1chp4-channelconfig.xml
===================================================================
RCS file: /cvsroot/asterisk/docs/volume-one/vm1chp4-channelconfig.xml,v
retrieving revision 1.8
retrieving revision 1.9
diff -C2 -d -r1.8 -r1.9
*** vm1chp4-channelconfig.xml 2 Oct 2004 17:03:20 -0000 1.8
--- vm1chp4-channelconfig.xml 2 Oct 2004 18:16:54 -0000 1.9
***************
*** 7,13 ****
>Introduction to Channels</title
><para
! >Channels are how an Asterisk system connects calls together. They can be thought of like the wires used by old phone operators that hooked calls together. The dialplan (Chapter 5) links these channels together and routes calls through them. As all forms of calls create a channel of some sort, they play a vital role in developing your Asterisk installation.</para
><para
>Channels come in all kinds of different formats from analog phone lines from your telephone company (FXO, FXS, PRI, BRI) to completely IP (SIP, IAX, etc). Asterisk transforms all of these channels into a kind of pipe for your call to flow through, and the pipes are connected together. It is important to remember that even though channels may vary in terms of technology and delivery, they are all just a channels, and channels can be connected to make a call.</para
></sect1
><sect1
--- 7,19 ----
>Introduction to Channels</title
><para
! >Channels are the various paths which Asterisk connects together to create calls. Essentially, if you want a call to take place in an Asterisk, you will need at least one channel. Connecting callers to callees is done by connecting channels. The dialplan (Chapter 5) is how you define the rules which Asterisk follows to determine how to link channels together. Before we can build a dial plan, we will need to determine what kind of channels we need, and configure them to be available to the system.</para
><para
>Channels come in all kinds of different formats from analog phone lines from your telephone company (FXO, FXS, PRI, BRI) to completely IP (SIP, IAX, etc). Asterisk transforms all of these channels into a kind of pipe for your call to flow through, and the pipes are connected together. It is important to remember that even though channels may vary in terms of technology and delivery, they are all just a channels, and channels can be connected to make a call.</para
+ ><para
+ >Asterisk is an extremely flexible and powerful PBX in large part because of the way it handles channels. In many older, proprietary PBXs, different channels have completely different ways of communicating. Station ports, Trunk ports and IP ports are so different that it requires years of training to figure out how to creatively connect them together. Indeed, it could be argued that becoming an expert on a particular PBX is mostly becoming intimately aware of it's limitations, and learning creative kludges to get around those limitations. Asterisk changes all that.</para
+ ><para
+ >Wherever possible, Asterisk allows you to treat any channel type in the same manner as any other channel type. Whether you are connnected to an analog set on an FXS port, or an IAX channel to your favourite VSP, the functions available to you are the same. This puts a greater responsibility on you the designer, as Asterisk will happily allow you to create something that is not workable. But it also means that Asterisk is able to be flexible as no other PBX can be.</para
+ ><para
+ ></para
></sect1
><sect1
***************
*** 15,24 ****
>FXO and FXS</title
><para
! >Foreign eXchange Station (FXS) channels are what your phone company provides to the wall of most homes or small businesses. It is the traditional flat analog telephone line. Since they provide dialtone, Asterisk can use an FXS channel to hook a basic analog phone set to the system to use for making and recieving calls.</para
><sect2
><title
>FXS</title
><para
! >If you have a Digium card that can provide an FXS channel, like the TDM400P, it can be configured in <filename
>zapata.conf</filename
> as follows:</para
--- 21,52 ----
>FXO and FXS</title
><para
! >The Terms FXO and FXS are terms referring to what the telephone companies called Foreign eXchange (or FX) circuits. The original purpose of an FX circuit was to allow an analog phone at a remote location to be connected to a PBX somewhere else. An FX circuit has two ends (the Station end, where the telephone is, and the Office end, where the PBX is). The confusing part about understanding FXO and FXS is that the cards are not named by what they do, but rather by what is connected to them. An FXS card, therefore, is a card that you connect a Station to. If that is so, you can see that an FXS card will need to behave like a central office in order to do it's job. Similarly, an FXO card connects to a Central Office, which means it will need to behave like a station (a modem is a classic example of an FXO device).</para
><sect2
><title
>FXS</title
><para
! >Foreign eXchange Station (FXS) channels are exactly the same as the traditional analog line your phone company provides to most homes or small businesses. Among other things, FXS channels have to provide:</para
! ><itemizedlist
! ><listitem
! ><para
! >Dial tone</para
! ></listitem
! ><listitem
! ><para
! >Ringing voltage</para
! ></listitem
! ><listitem
! ><para
! >DTMF (touch tone) detection</para
! ></listitem
! ><listitem
! ><para
! >Message waiting</para
! ></listitem
! ></itemizedlist
! ><para
! >In Asterisk, when you configure a Digium card that can provide an FXS channel (such as the TDM400P with FXS cards installed), you will need to define parameters that are relevant to an FXS card. <emphasis
! >Most importantly, you need to remember that an FXS card provides the sitgnalling of a central office</emphasis
! >. It can be configured in <filename
>zapata.conf</filename
> as follows:</para
***************
*** 29,40 ****
context=default
switchtype=national
! signalling=fxo_ks ; This is the signaling we're recieving not the one we're
! ; providing. ie. We get are providing an FXS signal so we
! ; are recieving an FXO signal.
channel => 1
</programlisting
></informalexample
><para
! >This does not of course contain all of the options but it sets up a simple FXS channel. It's important to remember that the signalling is always the signal you are recieving from the connected device, not the signal you are providing. The name of the device type (FXS) is the type of signal you are providing. This is confusing to some people, so it's defintely something to look out for.</para
></sect2
><sect2
--- 57,79 ----
context=default
switchtype=national
! signalling=fxo_ks ; This describes the function the card is providing. Since an FXS card performs the functions of a Central
! ;office (providing dial tone, ring voltage, message waiting, etc), we specify that the signalling we want to provide
! ;is that of a central <emphasis
! >O</emphasis
! >ffice - thus FXO_KS is the signaling. It's an FX<emphasis
! >S</emphasis
! > card, because you connect <emphasis
! >S</emphasis
! >tations to it, but it needs to
! ;provide the functions of a central <emphasis
! >O</emphasis
! >ffice, so the signalling has to be FX<emphasis
! >O</emphasis
! >.
channel => 1
</programlisting
></informalexample
><para
! >This does not of course contain all of the options but it sets up a simple FXS channel. Remember that the name of the device type (FXS) is the device that is connecting to you, so you have to assume the opposite characteristics. If I am an FXS card, I have to behave like a central office, if I am an FXO card, I have to behave like a station (a telephone set).</para
></sect2
><sect2
***************
*** 44,48 ****
>The main difference in the settings that are provided above when configuring an FXO channel instead of an FXS channel is signalling. Of course an FXO channel will get plugged into something that provides an FXS channel (like the phone company).</para
><para
! >In the zapata.conf we set up the channel as follows:</para
><informalexample
><programlisting
--- 83,87 ----
>The main difference in the settings that are provided above when configuring an FXO channel instead of an FXS channel is signalling. Of course an FXO channel will get plugged into something that provides an FXS channel (like the phone company).</para
><para
! >In the zapata.conf we set up the channel as follows (the previous :</para
><informalexample
><programlisting
***************
*** 51,57 ****
context=default
switchtype=national
! signalling=fxo_ks ; This is the signaling we're recieving not the one we're
! ; providing. ie. We get are providing an FXS signal so we
! ; are recieving an FXO signal.
channel => 1
signalling=fxs_ks
--- 90,107 ----
context=default
switchtype=national
! signalling=fxo_ks ; This describes the function the card is providing. Since an FXS card performs the functions of a Central
! ;office (providing dial tone, ring voltage, message waiting, etc), we specify that the signalling we want to provide
! ;is that of a central <emphasis
! >O</emphasis
! >ffice - thus FXO_KS is the signaling. It's an FX<emphasis
! >S</emphasis
! > card, because you connect <emphasis
! >S</emphasis
! >tations to it, but it needs to
! ;provide the functions of a central <emphasis
! >O</emphasis
! >ffice, so the signalling has to be FX<emphasis
! >O</emphasis
! >.
channel => 1
signalling=fxs_ks
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