T38Fax Blog

Why Power-T.38 from

Posted by Darren Nickerson on Sep 24, 2018 10:06:50 AM

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Our Power-T.38 product is similar to the SIP trunks you might purchase from another VoIP Service provider, with one significant difference - our SIP trunks are not only guaranteed to offer astoundingly reliable T.38 Fax Over IP call termination and origination, but that's really all they're meant to do. These purpose-built trunks are also competitively priced, making them suitable to everyone from the largest telecommunications carriers to the single home office fax machine connected with an analog telephone adapter (ATA).

We understand that you have many choices in today's crowded telecommunications market, so here are a few reasons you should give Power-T.38 a try:

  1. We do T.38 correctly. Almost nobody else does. We know, we looked!
  2. We support facsimile ECM (Error Correction Mode). You need it, and we insist on it.
  3. The largest SIP carriers don't understand T.38 at all - they're voice people.
  4. T.38 Fax Over IP is an elegant, extremely effective solution to a very real problem.
  5. It's free to try us, we even give you $25 and unlimited support from true fax experts.

We'll discuss each of those points in more detail, below. 

First of all, we really are the only provider of reliable T.38 FoIP service. We know this because we spent years looking for one for our own fax server software customers to use. Our parent company, iFAX Solutions, is an independent software vendor (ISV) that sells HylaFAX Enterprise, one of the world's most popular UNIX-based fax server software products. HylaFAX Enterprise includes the industry's most widely deployed T.38-aware SIP stack (SR140), which means that our customers have been able to do T.38 FoIP for well over 5 years now. In all that time, despite countless R&D projects to evaluate various SIP trunking services that claim to support T.38, we have been unable to find a single one that we could recommend to our customers.

The second point is a biggie. Fax is just not fax without Error Correction Mode (ECM). This obscure but vital feature of the T.30 facsimile protocol basically checks to make sure the other side has an exact pixel for pixel copy of the image being transmitted, and resends any missing or corrupted data before moving on to the next page. Without ECM you have no guarantee the other side is going to be able to read the fax at all, and yet there is a very common misunderstanding within the VoIP industry that ECM should be disabled when T.38 is being used. As fax purists, we will never recommend disabling ECM, and we will never certify a T.38-capable device as interoperable with our service unless it is capable of ECM error correction during a T.38 session.

Third, most VoIP service providers are really just repackaging and reselling the same three or four top-tier carriers' service, and not a single one of those carriers knows how to do T.38 correctly. Their implementations lack important features, and those features they do include are poorly implemented. The carriers know this, for the most part, but they're not movitated to improve. The demand for fax is just such a small percentage of their overall traffic, and the engineering and signal processing improvements they'd need to make are just too extensive. Most customers aren't experienced enough in fax themselves to recognize these shortcomings and call them on it, so everyone ends up using the same fundamentally broken T.38 FoIP service providers and we all end up spending countless hours on the telephone trying to lower the baud rate to 9600, turn features on and off, occasionally sacrificing a small animal in the vain hope that faxing will suddenly become reliable.

Fourth, the T.38 Fax Over IP protocol was invented to permit the transmission of faxes over a packet switched network (such as the Internet) where lost packets and variable latency (known as jitter) are the norm. Those conditions aren't a huge problem for voice conversations, but they're very disruptive to fax transmissions! When correctly implemented, T.38 is a very powerful, even elegant solution to these problems. There is absolutely no reason to settle for any more errors using T.38 than you have come to expect from traditional PSTN phone lines. 

Finally, it's free to try our service. In fact, we pay you to do so! We'll load your account up with $25 worth of free calling, and if you experience any problems at all we'll give you as much free support as you can handle. Our support ninjas are fax and SIP specialists, and I'm confident they'll exceed your expectations. 
See Our Free Trial Offer

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