[asterisk-users] Understanding of SIP Info Messages

[robb]

How are SIP Info Messages interpreted by asterisk as far as I 
understand, there are 17 different DTMF messages possible via sip info

DTMF 1,2,3,4,5,6,7,8,9,0 also A,B,C,D,E,F and Flash
, are any of these interpreted by asterisk, as I cannot seem to get 
asterisk to use the Flash information to put a call on hold so that it 
can be transferred, If I'm barking up the wrong tree could someone point 
me in the right direction, I'm using the latest asterisk 1.4

Thanks for your help

Robb