Add two rj 11 ports to your computer through usb for dial up internet and fax communication compatible with usb computer systems dual modem 2 port rj 11 fax modem dial up internet modem 2 port modem 56k dual port modem 2x rj11 modem usb modem turn a pc into a fax machine capable of sending and receiving faxes compatible with v 17 v 29 v 27 v 21 ch 2 eiatia 578 class 1 and t 31 fax class 1 0 fax modes use one port for 56k internet and the other for fax communications