HylaFAX is an enterprise-class system for sending and receiving facsimiles as well as for sending alpha-numeric pages.

The A01-PU3 is an usb PSTN modem that support the CDC ACM standard, and it works great on Linux!

On Debian you can easily setup an Hylafax Server installing it by:
<pre lang="bash">aptitude install hylafax</pre>
And configure your fax device with faxaddmodem:
<pre lang="bash">faxaddmodem /dev/ttyACM0</pre>

At this point, the faxserver was correctly receiving faxes but the sending was constatly failing due to no carrier errors:
<pre lang="none">Nov 16 12:18:09 hylafax FaxSend[8506]: SEND FAILED: JOB N DEST XXXXXXX ERR [2] No carrier detected</pre>
You should add to /etc/hylafax/config.ttyACM0 for fixing the problem:
<pre lang="none">ModemResetCmds: ATX3</pre>

You can find other useful information on:
DebianWiki
HylaFax Documentation
HylafaxFax Desktop Clients