Installation is made on Linux server on real or virtual machine. T.38 software modems and SIP lines with Т.38 support are used for connection to Avaya IP PBX. In this way physical modems are not used and PSTN lines could be of any kind.
Hylafax is a fax server allowing individual virtual phone numbers for each user. Incoming faxes are delivered as PDF files at the email address of the user and outgoing - through client application for Windows oe Linux OS. In this way no paper is needed.
Using fax server helps lowering the expenses and getting better fax managing.