function add_extension(a){
	// add extension 'a' in extensions.conf 
	// add 'exten => a,1,Queue' to default
	var opt0 = {
		method: 'get',
		asynchronous: true,
		onSuccess: function() { 
			return true;	
		},
		onFailure: function(t) {
			gui_alert("Config Error: " + t.status + ": " + t.statusText);
			return false;
		}
	};
	uri0[0] = build_action('append', 0, specialcontext ,'exten', a+',1,Goto(Queues,${EXTEN})' );
	uri0[1] = build_action('append', 0, queues ,'exten', a+',1,Answer()' ) ;
	uri0[2] = build_action('append', 0, queues ,'exten', a+',n,Playback(sales&for-quality-purposes&this-call-may-be-monitored-or-recorded)' );
	uri0[3] = build_action('append', 0, queues ,'exten', a+',n,GotoIf($["${CONTEXT}"="from-internal"]?USERCID:SETCID)' );
	uri0[4] = build_action('append', 0, queues ,'exten', a+',n(USERCID),Macro(user-callerid,)'  );
	uri0[5] = build_action('append', 0, queues ,'exten', a+',n(SETCID),Set(CALLERID(name)=${CALLERIDNAME})' );
	uri0[6] = build_action('append', 0, queues ,'exten', a+',n(ID),Playback(pls-enter-account)' );
	uri0[7] = build_action('append', 0, queues ,'exten', a+',n,Read(acct,then-press-pound)' );
	uri0[8] = build_action('append', 0, queues ,'exten', a+',n,SayDigits(${acct})' );
	uri0[9] = build_action('append', 0, queues ,'exten', a+',n,Background(if-this-is-correct-press)' );
	uri0[10] = build_action('append', 0, queues ,'exten', a+',n,SayDigits(1)' );
	uri0[11] = build_action('append', 0, queues ,'exten', a+',n,Background(if-this-is-incorrect-press)' );
	uri0[12] = build_action('append', 0, queues ,'exten', a+',n,SayDigits(2)' );
	uri0[13] = build_action('append', 0, queues ,'exten', a+',n,Read(res,then-press-pound,)' );
	uri0[14] = build_action('append', 0, queues ,'exten', a+',n,GotoIf($["${res}"="1"]?ACCT:ID)' );
	uri0[15] = build_action('append', 0, queues ,'exten', a+',n(ACCT),Set(CALLERID(number)=${acct})' );
	uri0[16] = build_action('append', 0, queues ,'exten', a+',n,Set(MONITOR_FILENAME=/var/spool/asterisk/monitor/q${EXTEN}-${TIMESTAMP}-${UNIQUEID})' );
	uri0[17] = build_action('append', 0, queues ,'exten', a+',n,Queue(${EXTEN}|t|||300)' );
	uri0[18] = build_action('append', 0, queues ,'exten', a+',n,Voicemail(u${EXTEN})' );
   var x=0;
	for(x;x<uri0.length;x++) {
			opt0.parameters="action=updateconfig&srcfilename=" + encodeURIComponent("extensions.conf") + "&dstfilename=" + encodeURIComponent("extensions.conf") + uri0[x];
	tmp0 = new Ajax.Request(asterisk_rawmanPath, opt0);
        }
}