Fax machines are supported in a similar manner to other analog devices in Lync, but require a bit more planning and configuration. Specifically, there is a parameter on the New-CsAnalogDevice cmdlet called
AnalogFax that must be set to
$true for any fax machines. The reason for this is to ensure that the media for a fax call is never routed through Lync.
For an analog phone it’s not a big problem if the media stream runs through Lync. The Mediation Server can transcode G.711 audio from a gateway to RTAudio and back again if needed, but the issue is that the Mediation Server cannot handle the T.38 fax tones properly. So the point of identifying fax machines is to indicate to Lync Server that it must remain out of the media path and ...