server 2003 and two modem line

i’ve sbs 2003 running windows fax service with one modem and one phone line that dedicated to send and receive fax’es.. now.. i want to install another modem on the server and buy another phone line for it, because i want to dedicate one modem for recieve mode and one for sending. what should i configure on the sbs server in the fax service console? thanks dror