[Freeswitch-users] tone_detect and dinging

I use this in my dialplan before a bridge ... <action application="set" data="instant_ringback=true"/> <action application="ring_ready"/> <action application="tone_detect" data="fax 1100 r +5000 transfer 'receivefax XML features' 1" /> .... but no ring is back to the caller. if I remove tone_detect the ringback is working again. is anyone knows why ? Thanks