Thanks for your reply Anthony, But i think you didn't quite understand my question. Custom Ring Back Tones (Early Media) is one of the features listed in FreeSWITCH features page and details of FreeSWITCH Early Media mode is detailed in FreeSWITCH wiki : http://wiki.freeswitch.org/wiki/Early_Media By pre-answer i mean picking a call in Early Media mode (Early media is the exchange of information before establishment of a connection) which mean on early media mode, even though an audio is playing like Custom Ring Back Tones, the call is not connected so the caller is not billed. The question again is how can the FreeSWITCH Early Media feature be used from mod_httapi? Also, is there any performance benefit for using mod_httapi over a framework like Plivo that provide RESTFul features to FreeSWITCH? Regards Karl C.