T38 fax

Hi Group,

Question, is T38 generally considered to be a production reliable protocol for faxing now or is it still considered experimental? I have a potential opportunity to sell a new phone system to a customer on the basis of ROI. They currently have 15 copper POTS lines dedicated to faxing only. They are paying somewhere in the neighborhood of $40 per line.

I believe I could make the sale for an all new phone system on the basis of eliminating that $600 in fax phone lines alone, but I don’t want to go down this path if the technology is not going to work reliably.


Many more details are needed for a comment.

1 - What software are you “selling” them
2 - Is this fax transmission or reception
3 - How are you going to implement the fax connection (FAX machines to ATA or DAHDI interface? FAX Pro module? Other 3rh party software)?
4 - What type of circuits to server (SIP, POTS, PRI?)

You ask good questions but the truth is I won’t know for sure until after I meet with them this week to discuss needs. I’ll do my best to give you an idea.

1.) Either digium switchvox or freepbx with paid modules
2.) Both send and receive fax with conventional fax machines
3.) Some type of hardware fxs gateway, probably a stand alone device that can handle 16 ports.
4.) SIP for sure, the goal is to eliminate a whole bunch of (15 at least) pots lines, the cost of the pots is what is driving the sale.


1 - We don’t discuss Switchvox here, this is a FreePBX forum
2 - Ok
3 - Ok
4 - Even with other issues I don’t see the savings. POTS lines are flat rate inbound. SIP is metered

The only folks I have seen that are happy with SIP/FAX are casual FAX users.

Even with a PRI then SIP to branch office I was not able to make the solution reliable enough.

Lastly, without FreePBX reseller experience and an extensive background deploying Asterisk/FreePBX you are going to spend an incredible amount of time coming up to speed or utilizing paid support and as I said in the end you aren’t going to have the reliability they have with the POTS service.

Sorry to be the bearer of bad news but analog data transmission (Modems/FAX/Credit Card Machines/Alarm Systems) are a bad mix for VoIP.

ok thanks.

Keep in mind I am just one opinion, but that is my experience.

Take a look at http://www.vitelity.com/services_vfax/ . Reliability is outstanding, though it’s not cheap ($0.03/min + USF, in or out) and may not save much for heavily used lines. There is no VoIP anywhere in the path between the fax machines. It also provides means to gradually migrate to an improved workflow that doesn’t require printing out documents to fax them. A downside is that your PBX is not in the path; usage data for accounting or billing purposes must be downloaded from Vitelity. Though I don’t believe all they say, here is their pitch on why it’s better than T.38: http://www.vitelity.com/blog/2013/04/why-t-38-does-not-solve-the-fax-problem/

Next step down, look at Callcentric for T.38. I’ve had good luck (though with single fax lines) using Linksys SPA2102 and Obihai OBi202 adapters. It’s not cheap, either ($0.02/min.), and you’ll probably be limited to 9600 bps, so calls will be longer than with POTS. Inbound on non-toll-free numbers is free. If you have a suitable adapter, you can get an account and do a lot of testing for $10.

Dirt cheap, Alcazar Networks supports T.38. You’ll probably average less than $0.005/min. You should definitely test this before proposing it to your customer. You get a free 24-hour trial at signup, or fund your account for $25 and test at a leisurely pace.