grc/misc_utils/gsm_burst_source.xml

<?xml version="1.0"?>
<block>
  <name>Burst source</name>
  <key>gsm_burst_source</key>
  <import>import grgsm</import>
  <make>grgsm.burst_source($filename)</make>

  <param>
    <name>Source file</name>
    <key>filename</key>
    <value>/tmp/bursts</value>
    <type>file_open</type>
  </param>

  <source>
    <name>out</name>
    <type>message</type>
  </source>
</block>