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

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

<info>
  <title>Local Repeater Operation</title>
</info>

<para>
  One central objective of DMR is to be repeater transparent. That is, it does not matter which 
  repeater you use. You will always be able to reach the same groups and be always reachable 
  through the same means (private or group call). This concept is violated by the talk groups 8
  &amp; 9. The are the regional and local talk groups.
</para>
 
<example xml:id="figIntroTG9TG8">
  <title>Two regions with two repeaters each.</title>
  <mediaobject>
    <imageobject><imagedata fileref="fig/repeater_local.png" width="10cm" align="center"/></imageobject>
  </mediaobject>
</example>

<para> 
  The talk group 9 (TG9) is the so-called local talk group. Group calls to that talk group are not 
  forwarded though the network and only retransmitted locally. Usually <quote>locally</quote> means
  only the repeater. Sometimes, however, these calls are also forwarded to other repeaters 
  nearby. This case is shown in <xref linkend="figIntroTG9TG8"/> on the left side. Here DM3MAT sends 
  a group call to TG9 via the repeater DB0ABC. This call is not forwarded to any other repeater and 
  thus is only received in the local area around the repeater. DL1XYZ is in that local area and may 
  receive that call if he configured his radio to receive calls from the TG9.
</para>

<para>
  The talk group 8 (TG8) is the so-called regional talk group. A call to that talk group is usually 
  forwarded to all repeaters within a specific region. Which repeaters are part of a 
  <quote>region</quote>, is a decision of the repeater administrators. So it is hard to predict to 
  which repeaters a regional call gets forwarded. In <xref linkend="figIntroTG9TG8"/> on the right
  side, DL3XYZ sends a group call to TG8 to the repeater DB0GHI. This call gets forwarded to 
  all repeaters in the <quote>region</quote>. In this case, also to the repeater DB0JKL within the
  same region. Therefore, all participants within that region are able to receive the group call 
  if they configured their radios accordingly. In this example, not only DL4XYZ received the call 
  but also DL5XYZ who is not close to the repeater DB0GHI and would have missed a group call to the 
  local talk group.
</para>
</section>
