gateway dialplan is:

<extension name="mytelco">
        <condition field="destination_number" expression="^987(\d+)$">
            <action application="set" data="effective_caller_id_number=46xxxxxxxx"/>
            <param name="caller-id-in-from" value="true"/>
            <action application="set" data="record_link=${strftime(%Y-%m-%d-%H-%M-%S)}_${destination_number}_${caller_id_number}.wav"/>
            <action application="record_session" data="/var/www/html/freeswitch/recordings/${record_link}"/>
            <action application="lua" data="/etc/freeswitch/scripts/beep_detection-from-call-v0.1.2.lua $1 ${record_link}"/>
            <action application="hangup"/>
        </condition>
    </extension>
    
    
    
file beep_detection-from-call-v0.1.2.lua

#!/usr/local/bin/lua

DNID = argv[1]

if session:ready() then
   session:sleep(1000)
   session:execute("avmd_start", "inbound_channel=1,outbound_channel=0,sample_n_continuous_streak=10,sample_n_to_skip=0,debug=1,report_status=1")

    session:execute("bridge", "{execute_on_answer=lua /etc/freeswitch/scripts/on_answer-v0.3.lua " .. uuid .. "}sofia/gateway/mytelco/" .. DNID)

    session:execute("avmd_stop","")

end --if



file on_answer-v0.3.lua

#!/usr/bin/lua

uuid_original = argv[1]

api = freeswitch.API()

reply = api:executeString("bgapi uuid_broadcast " .. uuid_original .. " /usr/share/asterisk/sounds/en/dennis-ivan.gsm both")

freeswitch.consoleLog("INFO","==============================================")
freeswitch.consoleLog("INFO","API reply is:" .. reply)
freeswitch.consoleLog("INFO","==============================================")