Outgoing Faxes Over VoIP: Suggestions And Requests

I’ve spent the past few days trying to figure out how to send a multi-page fax from my Brother MFC-8500 over my BroadVoice VoIP account and its Sipura SPA-1001 adapter (see here for a thorough explanation of the substantial technical issues involved in this seemingly trivial task). I ‘think’ I’ve nailed down a sustainably successful configuration, which I’ll detail below and which I suspect is more broadly applicable to other fax machines, VoIP providers and SIP adapters, but I welcome your ideas on other things your fellow readers and I can try.

• Discussion threads like this one suggest that you should manually configure your fax machine to not transmit at rates above 9600 baud. Unfortunately, the MFC-8500 doesn’t have explicit user baud rate control; the owner’s manual notes that the fax modem speed is "14400-2400 bps" with "Automatic Fallback". However, the MFC-8500 offers an Overseas Mode that cryptically "Adjusts for sometimes difficult overseas transmissions" and "Makes temporary changes to the fax tones to accommodate noise and static on overseas phone lines." Guided by advice like this, I tried it, and it seems to help. Note that, at least on the MFC-8500, "After you send a fax using this feature, the feature turns itself off." It also drastically slows per-page outgoing fax speeds. Then again, though, when the alternative is no outgoing fax speed…
• Wholly devote your broadband pipe to the fax task at hand. No email sending or receiving, web surfing or other LAN or WAN activity (no matter how bandwidth-and latency-miniscule you think it might be) while fax transmission is in progress, if at all possible.
• You might think that, to aid in the above aspiration, a VoIP-cognizant QoS optimizer such as Hawking’s HBB1 or Linksys’ OGV200 would be helpful. You’d think (and I did)…but if my experiments’ results are broadly applicable, you’d be wrong. I couldn’t get fax transmissions to succeed until I removed the OGV200 intermediary from the link between my DSL modem and router.

FYI I didn’t hack any of the Sipura SPA VoIP adapter’s settings, although I do know the unit’s administrator password.

Followup: one of the commenters has a good point; stick to standard resolution scans, as well, for highest statistical probability of outgoing fax completion success.