Technical Question about VOIP hardware

[Damo-T]

Can anyone assist please?????
A friend of mine would like to do the following, can anyone tell me if it is possilbe to modify the Lynksys VOIP adapter to achieve it or is there any other product out there which may do? Any help would be greatly appreciated. My friend is experienced in electronic equipment but not so much the IT/VOIP side of things.

I should like the two phone ports to operate independently of each other in either of two modes. One mode would be no different from the present, unmodified state, which allows a standard telephone to provide the normal speech, dial and ring functions to a remote location via VOIP.
The second mode would provide separate connections for send and receive signals on the inner and outer pairs of the phone port connector, and would be selected under external logic control or by sensing a load change on the phone ports when the audio circuitry replaces the telephone. Basically this would allow the two phones at the Lynksys end to speak to each other as well.
I hope this makes sense, I am not very technical on this kind of thing myself so if you need further information, please let me know.
Thanks in advance if you are able to assist.