Asterisk and rtc modem

I’m wondering if is it possible to use your software like that :

Internet High Speed Line -> An Linux workstation with Asterix connected to one SIP provider like voipbuster -> Connect a standart phone with a cross cable to the rj11 connector of an old RTC modem ( the modem connected with rs232 connector to the computer and the phone directly to the rj11 line of the modem )

Do you think it is possible ? I remember that it was possible to share datas between to old rtc modems, so I think it could be possible.

Do you understand ( sorry for my badly english )
Thank you for your software
best regards