Index: doc/userguide/userguide.xml
===================================================================
RCS file: /home/cvs/gateway/doc/userguide/userguide.xml,v
retrieving revision 1.359
diff -a -u -r1.359 userguide.xml
--- doc/userguide/userguide.xml	9 Mar 2010 14:30:36 -0000	1.359
+++ doc/userguide/userguide.xml	15 Mar 2010 18:06:16 -0000
@@ -3975,7 +3975,45 @@
    It is recommended to use <literal>keepalive</literal> variable, in order to 
    automatically reconnect in case of network connectivity problems.</para>
 
+   <para><emphasis>About modem initialization:</emphasis>
+   This question has frequented much user lists. It usually comes in 2 forms:
 
+   <orderedlist>
+     <listitem><para>My modem doesn't receive or transmit SMS.</para>
+        <para>In its current implementation, the at driver will panic if it
+           cannot find the modem device and bearerbox won't start. This can
+           happen either because the wrong modem device is configured or the
+           device has no write access for kannel's user.</para>
+        <para> In the first case use system logs to discover where is your
+           modem assigned to:</para>
+        <para>grep tty /var/log/messages</para>
+        <para>Then verify that this is indeed your GSM modem device by
+           connecting to it with minicom or wvdial and issuing a few AT
+           commands. Wvdial is preferrable, since it can also give you a
+           working <literal>init-string</literal></para>
+        <para>In the second case you need to give write access to kannel user.
+           This is no problem if you run kannel as root, but it is not
+           recommended to do so. In Ubuntu linux you just need to assign kannel
+           user to group "dial". In other systems you can either chmod 666
+           /dev/modem or preferably chmod 664 /dev/modem; chgrp <emphasis>group
+              </emphasis> /dev/modem; usermod -G <emphasis>group</emphasis>
+              <emphasis>kannel user</emphasis>.</para>
+     </listitem>
+     <listitem><para>My modem doesn't receive DLRs or SMS.</para>
+        <para>Modem doesn't know how to treat incoming messages. This is
+           configured at the  <literal>init-string</literal> with the <emphasis>
+              +CNMI=x,x,x,x,x</emphasis> command. X's are decimal numbers and
+           CNMI (Command New Message Indication) specifies to the modem what to
+           do with incoming messages. There is no hard rule about its values.
+           They are model and manufacturer specific. Best to consult modem
+           manual or manufacturer's web site. Failing that, wvdialconf might
+           give a working CNMI. Finally see modems.conf for examples and try
+           different values. Some Nokia phones do not support this command, but
+           are ready to transmit incoming messages from the start. This setting
+           should be consistent with <literal>sim-buffering</literal> and
+           <literal> message-storage</literal> values.</para>
+     </listitem>
+  </orderedlist>
 </sect2>