[Asterisk-doc] Added some ISDN documentation

[Jens Kübler]

comments, suggestions welcome.

According to the webpage this seems the correct place to post this patch.

Jens Kübler

now with correct identity
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Index: vm1chp4-channelconfig.xml
===================================================================
RCS file: /cvsroot/asterisk/docs/volume-one/vm1chp4-channelconfig.xml,v
retrieving revision 1.15
diff -u -r1.15 vm1chp4-channelconfig.xml
--- vm1chp4-channelconfig.xml	1 Feb 2005 22:57:34 -0000	1.15
+++ vm1chp4-channelconfig.xml	27 Feb 2005 11:34:16 -0000
@@ -307,6 +307,97 @@
 </sect3>
 </sect2>
 </sect1>
+
+<sect1>
+<title>
+ISDN</title>
+<sect2>
+	<para>
+	The Integrated Services Digital Network (ISDN) is a major telephone standard throughout the world.
+	There are lots of protocol variants out there at different network layers and this manual shall give
+	you only the two most used variants.
+	</para>
+	<sect3>
+		<title>
+		Primary Rate ISDN (PRI)
+		</title>
+		<para>
+		Primary Rate ISDN is a 32 channel (24 for the US) ISDN line which is used normally for
+		large corporations and central offices. One of those 32 channels is used for synchronisation
+		and another one is used to setup the  D - channel which transfers the signalling information
+		for incoming and outgoing calls. So you remain with 30 B - channels that can actually be used
+		for speech oder other ISDN services.
+		</para>
+		
+		<para>
+		Asterisk has support for PRI through zap channels. You need to take a look at the Compile->Zaptel
+		chapter to figure out how hardware is setup for this channel type.
+		If you're finished with that you have to configure <filename>/etc/asterisk/zapata.conf</filename>
+		</para>
+		<informalexample>
+		<programlisting>
+		[channels]
+		language=de                 ; Default language
+		context=default             ; Default context when dialing
+		switchtype=euroisdn         ; This is the D - channel protocol (EDSS1 in this case)
+		pridialplan=national        ; PRI Dialplan
+		prilocaldialplan=national   ; PRI Local Dialplan
+		signalling=pri_cpe          ; we are not a service provider / telco , so we will choose pri_cpe
+		group = 1
+		callgroup = 1
+		pickupgroup = 1
+		channel => 1-15,17-31       ; configure where B - channels are, D - channel is 16
+		</programlisting>
+		</informalexample>
+		<para>
+		The hardware setup is responsible for synchronizing the line and asterisk starts the D - channel.
+		After that you're ready to call Zap channels. Consult "Configure Dialplans" chapter for more
+		information on how to call Zap channels.
+		</para>
+	</sect3>
+	<sect3>
+		<title>
+		Basic Rate ISDN (BRI)
+		</title>
+		<para>
+		Basic Rate ISDN is most commonly used for small offices and home usage. You get two B-channels
+		for voice and other ISDN services and a D-channel used for signalling incoming and outgoing calls.
+		You may have heard also the terminology S0 in that case. Asterisk supports three different
+		channel types to get ISDN to work.
+		There are two major differences in the way telcos provide this kind of ISDN service.
+		For most homes this is the "Point to Mulitpoint" (PTMP) service which gives you three telephone
+		numbers (MSN).
+		For most of the smaller offices this is the "Point to Point" service which gives you just one
+		number but all
+		following numbers are handled by your PBX which in our case is Asterisk.
+		This feature is called "Direct Inward Dialing" (DID).
+		</para>
+		<sect4>
+		<title>Modem Channel</title>
+		<para>
+		There is support for ISDN devices from kernel side through the interfaces <filename>/dev/ttyIx</filename>
+		where as x is the number of the device line.
+		</para>
+		</sect4>
+		<sect4>
+		<title>Common Application Programming Interface (CAPI)</title>
+			<para>
+			CAPI is a well known standard application programming interface for ISDN cards.
+			There is third-party support for this channel type from Junghans.net. Check them out for
+			further reference.
+			</para>
+		</sect4>
+		<sect4>
+		<title>mISDN</title>
+			<para>
+			This is the new ISDN interface for 2.6 kernels. This channel is not provided by Asterisk
+			source itself but a third-party company named Beronet. Check them out for further reference.
+			</para>
+		</sect4>
+	</sect3>
+</sect2>
+</sect1>
+
 <sect1>
 <title>
 Other Channel Protocols</title>