Codec Selection

Hi All,

I have one Carrier which is supporting only G.723.1,
how i can put in my extentions.conf to send calls to
this GW using G.723.1, because for Clients i can
specify the codec from sip.conf but i am little
confiuse how i can give specific codec for carriers.

i tried in my extentions.con like :

exten => _x.,1,Set(SIP_CODEC=gsm)

But still taking this codec option for sip.conf

your ideas will be appriciated.