Something

    <outboundProxy voIpProt.SIP.outboundProxy.address="" voIpProt.SIP.outboundProxy.port="5060" voIpProt.SIP.outboundProxy.transport="DNSnaptr"/>
    <alertInfo voIpProt.SIP.alertInfo.1.value="CUSTOM_1" voIpProt.SIP.alertInfo.1.class="8" />
    <alertInfo voIpProt.SIP.alertinfo.2.value="Ring Answer" voIpProt.SIP.alertInfo.2.class="4" />
    <requestValidation voIpProt.SIP.requestValidation.1.request="" voIpProt.SIP.requestValidation.1.method="" voIpProt.SIP.requestValidation.1.request.1.event="">

.........


<ringType se.rt.enabled="1" se.rt.modification.enabled="1">
         <DEFAULT se.rt.1.name="Default" se.rt.1.type="ring" se.rt.1.ringer="2" se.rt.1.callWait="6" se.rt.1.mod="1"/>
         <VISUAL_ONLY se.rt.2.name="Visual" se.rt.2.type="visual"/>
         <AUTO_ANSWER se.rt.3.name="Auto Answer" se.rt.3.type="answer"/>
         <RING_ANSWER se.rt.4.name="Ring Answer" se.rt.4.type="ring-answer" se.rt.4.timeout="2000" se.rt.4.ringer="2" se.rt.4.callWait="6" se.rt.4.mod="1"/>
         <INTERNAL se.rt.5.name="Internal" se.rt.5.type="ring" se.rt.5.ringer="2" se.rt.5.callWait="6" se.rt.5.mod="1"/>
         <EXTERNAL se.rt.6.name="External" se.rt.6.type="ring" se.rt.6.ringer="2" se.rt.6.callWait="6" se.rt.6.mod="1"/>
         <EMERGENCY se.rt.7.name="Emergency" se.rt.7.type="ring" se.rt.7.ringer="2" se.rt.7.callWait="6" se.rt.7.mod="1"/>
         <CUSTOM_1 se.rt.8.name="Custom 1" se.rt.8.type="ring" se.rt.8.ringer="5" se.rt.8.callWait="7" se.rt.8.mod="1"/>

.......

extensions.conf: 

[macro-page]
exten => s,1,ChanIsAvail(${ARG1}|js) ; j is for dump and s is for ANY call
exten => s,2,SIPAddHeader(Alert-Info: Ring Answer)
exten => s,3,Dial(${ARG1})
exten => s,4,Hangup
exten => s,102,Hangup

....

exten => 492,1,Macro(page,SIP/492)