[Freeswitch-users] isfocus parameter in Contact header

Hi all, I am relatively new to Freeswitch and I am looking for a way to add isfocus parameter in the Contact header of 200 OK (INVITE response) from the freeswitch. I found channel variable sip_contact_params that can be set in dialplan as below, but it doesnt seem to help. Am I missing something or doing something wrong here? <action application="answer"/> *<action application="set" data="sip_contact_params=isfocus"/>* <action application="conference" data="..." Please advise. Thanks Ramesh