Transfering a call when its in ringing state

I am using free PBX with asterisk 1.4 with PRI, the phone i am using are Polycom 601 & Grandstream.
now i want to transfer a call when it is not established i.e its in ringing state on zap. say i want to call XXXXXXXXXXX on pstn through zap and while its ringinng i want it to transfer it to a sip phone. this is not happening, the call can be transferred only when it is established.
the transfer keys on phone are not working, even the ## is not working.
where as i installed a plane asterisk where it is working
here is the dial plan of working plane asterisk

[globals]
CONSOLE=Console/dsp
TRUNK=Zap/g1
TRUNK=Zap/g2

[demo]
include => default

[local]
include => default

; For dial pad
exten => _9.,1,Answer
exten => _9.,2,Dial(Zap/g1/${EXTEN:1})
exten => _9.,3,Hangup

exten => 1710,1,Ringing
exten => 1710,2,Dial(SIP/710${EXTEN:4}|20|t)
exten => 1710,3,Hangup

/////////////////////////////////////////////////////////////////////
for freepbx
i have put

in genral settings
i have put
asterisk dial command option tr
asterisk dial outbound dial command option t

here is the extension_additional.conf

#include globals_custom.conf
CALLFILENAME = ""
DIAL_OPTIONS = tr
TRUNK_OPTIONS = t
DIAL_OUT = 9
FAX =
FAX_RX = system
FAX_RX_EMAIL = [email protected]
FAX_RX_FROM = [email protected]
INCOMING = group-all
NULL = ""
OPERATOR =
OPERATOR_XTN =

is there some thing i am missing to make it work, help needed despratly