<?xml version="1.0"?>
<block>
  <name>uplink_downlink_filter</name>
  <key>grgsm_uplink_downlink_filter</key>
  <category>GSM</category>
  <import>import grgsm</import>
  <make>grgsm.uplink_downlink_filter()</make>
  <sink>
    <name>in</name>
    <type>message</type>
    <optional>1</optional>
  </sink>
  <source>
    <name>downlink</name>
    <type>message</type>
    <optional>1</optional>
  </source>  
  <source>
    <name>uplink</name>
    <type>message</type>
    <optional>1</optional>
  </source>  
</block>