In dialplan I set ringback variable

      <extension name="setRingback" continue="true">
         <condition>
            <action application="set" data="ringback=${us-ring}"/>
         </condition>
      </extension>
And diaplan terminate call on extension

<extension name="agent_login">
   <condition field="${destination_number}" expression="^agent_login$">
      <action application="set"
              data="ignore=${callcenter_config(agent set status ${caller_id_number}@${sip_to_host} 'Available')}"
              inline="true"/>
      <action application="ring_ready"/>
      <action application="pre_answer"/>
      <action application="sleep" data="2500"/>
      <action application="answer"/>
      <action application="sleep" data="700"/>
   </condition>
</extension>

But ringback is not generaded. Why is it posible?

Sergey