Installation guide

140 Planning and Installation Guide ShoreTel 14.2
Planning Applications and Services Using a Fax Server
8
Fax Server Requirements
 Sufficient ports on ShoreTel voice switches
 Sufficient ShoreTel User Licenses
 Sufficient DID trunks to support both fax and voice DID for all users
Network Requirements
The network requirements for faxing over IP are more stringent than for voice over IP. For voice
communications, a 1% packet loss has negligible impact on voice quality. However, a 1% packet loss
for fax communications means a loss of approximately 3 lines per fax page. ShoreTel recommends
that packet loss not exceed 0.1% across the LAN and WAN when using fax servers with the ShoreTel
system.
Fax communications are also impacted by voice compression. Since fax machines typically require
19.2 Kbps, ShoreTel recommends that you use G.711 voice encoding for fax calls. For more
information on fax requirements, refer to ShoreTel IP Phones on page 166.
Fax Server Integration Details
Instead of requiring users to have two separate DID numbers — one for voice and one for fax — a
single DID line can handle voice calls and inbound/outbound faxing.
A user's extension, which can be 3, 4, or 5 digits, is sent to a fax server via in-band Dual Tone Multi
Frequency (DTMF) digits. The fax server uses this information to create a mapping between the user’s
extension and e-mail address.
Once configured, incoming fax calls are received at the user's phone extension. The fax server listens
for the fax tone, and takes over the call when the fax redirect radio button has been selected in
Director. When the fax transmission is complete, the loop current is automatically turned off to
terminate the fax call, and the and fax is forwarded to the associated e-mail address. Figure 25 shows
the flow for a fax call.
Note
The fax redirect feature will not work with calls that come in on SIP trunks.