Hello list, I able to send & receive faxes via SS7 link. but I have a small problem with "switch_core_media_bug". I noticed "Media bug" activate for first 10 seconds to 20 seconds against SIP channels. most of our customers use Tele/FAX option on Fax machines. that means ; they answer the call manually (as a voice call) If there was a fax then they activate Fax mode. the problem is FS can't detect CNG tones after 20 seconds, because "switch_core_media_bug" was removed from the particular channels. If the destination fax machine can generate CNG tones within 10 ~ 20 seconds Then FS can detect CNG tones and change in to T.38 mode. is there any way to increase the window of time (switch_core_media_bug) to listen for the CNG tones on SIP channels? This is my dialplan for G711(from PSTN/SS7 via SIP) to T.38(to SIP ATAs) ------>8-------- <extension name="g711_to_t.38"> <condition field="destination_number" expression="^1(0\d{8})$"> <action application="pre_answer"/> <action application="set" data="ringback=%(1000, 4000, 400.0, 400.0)"/> <action application="t38_gateway" data="peer"/> <action application="bridge" data="sofia/external/$1@192.168.11.53"/> <action application="hangup"/> </condition> </extension> This is my dialplan for T.38(from SIP ATAs) to G711(to PSTN/SS7 via SIP) ------>8-------- <extension name="t.38_to_g711"> <condition field="destination_number" expression="^(0\d+)$"> <action application="ring_ready" /> <action application="set" data="ringback=%(1000, 4000, 400.0, 400.0)"/> <action application="start_dtmf_generate" data="true"/> <action application="t38_gateway" data="self"/> <action application="bridge" data="sofia/external/$1@192.168.11.54:5070"/> <action application="hangup"/> </condition> </extension> ------>8-------- Thank you. Weera Suriya