[Asterisk-Users] rfc2833 cisco 7960 DTMF issue

[Sergio]

I'm having an issue sending DTMF to cisco

dialing this extension I should hear the dtmf tone
RTP playload 101 has been sent to the cisco phone, but no audio.

in the dialplan
exten => 8603,1,Answer(1)
exten => 8603,n,sipdtmfmode(rfc2833)
exten => 8603,n,SendDTMF(1|100)
exten => 8603,n,hangup()

sip.conf
dtmfmode=rfc2833

SIPDefault.conf
I did play with all possible settings for dtmf_outofband: avt, 
avt_always, none and 0,1 for dtmf_inband

nothing happens
cisco 7905g is working OK with this example
cisco 7960 firmware issue?
Any help?