<?xml version="1.0" encoding="UTF-8"?>

<section xml:id="introTalkGroup" 
         xmlns="http://docbook.org/ns/docbook" 
         xmlns:xlink="http://www.w3.org/1999/xlink" 
         xmlns:xi="http://www.w3.org/2001/XInclude">

<info>
  <title>Talk Group Operation</title>
</info>

<para>
  As mentioned in <xref linkend="introPrivateCalls"/>, DMR aims at being repeater transparent. That
  is, it does not matter which repeater is used for the operation. This is also true for talk 
  groups. In this section, I'll continue with the example of an OM at his holiday location, who wants
  to participate in his afternoon net. For example, the afternoon net is happening on the talk 
  group 2621 (Berlin/Brandenbug, BB). This talk group is usually statically subscribed on all 
  repeaters in the states Berlin and Brandenbug. That means that the local afternoon net can be 
  performed in this talk group without any additional action in this area. (see 
  <xref linkend="figIntroTG"/> top image).
</para>

<example xml:id="figIntroTG">
  <title>Talk group operation between countries</title>
  <mediaobject>
    <imageobject><imagedata fileref="fig/talkgroup_ex1a.png" width="10cm" align="center"/></imageobject>
  </mediaobject>
  <mediaobject>
    <imageobject><imagedata fileref="fig/talkgroup_ex1b.png" width="10cm" align="center"/></imageobject>
  </mediaobject>
  <mediaobject>
    <imageobject><imagedata fileref="fig/talkgroup_ex1c.png" width="10cm" align="center"/></imageobject>
  </mediaobject>
</example>

<para>
  For the OM at his holiday location, this it not true. An Italian repeater will certainly not 
  subscribe the BB talk group statically. Therefore, the OM at the holiday location will not hear 
  his afternoon net. He knows, however, when this net starts. So he can perform a group call to the that TG 
  shortly before the net starts (see <xref linkend="figIntroTG"/> second image). This will 
  subscribe the BB talk group temporarily at the holiday repeater (I0ABC). Now, the OM can hear and
  participate in the afternoon net. The subscription will be renewed whenever he starts a group 
  call to that TG.
</para>

<para>
  Once the OM subscribed the TG to the holiday repeater, he can participate normally at his 
  afternoon net. All other participants will not even notice that he is not in the area and is 
  participating from an italien repeater.
</para>

<table xml:id="tabIntroTG">
  <thead>
    <tr><td>Name</td> <td>Talk group number</td></tr>
  </thead>
  <tbody>
    <tr><td>Global</td> <td>91</td></tr>
    <tr><td>Europe</td> <td>92</td></tr>
    <tr><td>Germany</td> <td>262</td></tr>
    <tr><td>Mecklenburg-Vorpommern &amp; Sachsen-Anhalt</td> <td>2620</td></tr>
    <tr><td>Berlin &amp; Brandenburg</td> <td>2621</td></tr>
    <tr><td>Hamburg &amp; Schleswig-Holstein</td> <td>2622</td></tr>
    <tr><td>Niedersachsen &amp; Bremen</td> <td>2623</td></tr>
    <tr><td>Nordrhein-Westfalen</td> <td>2624</td></tr>
    <tr><td>Rheinland-Pfalz &amp; Saarland</td> <td>2625</td></tr>
    <tr><td>Hessen</td> <td>2626</td></tr>
    <tr><td>Baden-Württemberg</td> <td>2627</td></tr>
    <tr><td>Bayern</td> <td>2628</td></tr>
    <tr><td>Sachsen &amp; Thüringen</td> <td>2629</td></tr>
  </tbody>
  <title>Some talk groups</title>
</table>

<section>
<info><title>Cluster</title></info>
<para>
  In contrast to the regional talk group TG8, all other talk groups are reachable from everywhere 
  in the DMR network. This means, that the OM at his holiday location can easily participate in 
  his afternoon net from everywhere as described above. 
</para>

<para>
  If the net, however, is happening in the regional TG8, the OM at his holiday location cannot 
  participate. This talk group is only reachable from within the region. If the OM starts a call to
  TG8, he would only reach the region in italy and not the region at home.
</para>

<para>
  For this reason, some regional <emphasis>clusters</emphasis> of repeaters are linked to a
  so-called <quote>Cluster</quote>. These clusters provide <quote>normal</quote> talk groups for the 
  repeater within a region. These clusters are then also reachable from the outside. A list of 
  regional clusters and their associated talk group numbers can be obtained under 
  <link xlink:href="http://bm262.de/cluster/">bm262.de/cluster/</link>.
</para>
</section>

</section>