hi
i'm new in this topic like you and i didnt work with ibm(j323 or h323)
i'm worked with gjtapi and i can call and answer with gjtapi
i used "net.sourceforge.gjtapi.GenericJtapiPeer" as provider
and modem as service and config ZoomConexant modem to working with my modem
and when you want to working with serial or parallel in java you can use comm api(sun) or rxtx api
and config ModemIO for one of these (default is comm) and after that make a call or answer
in this situation i have problem that this style has dependency to modem and this provider has problem for working with media .

in this way im looking for a way that i have no dependency to hardware

you can get some information about j323 from here
http://www.alphaworks.ibm.com/tech/j323engine