Power-T.38 for Business
Your VoIP Migration Doesn't Have to Kill Your Fax
Power-T.38 delivers reliable T.38 Fax Over IP for businesses running ATAs, IP-PBXs, MFPs, and analog fax machines. One fax-optimized SIP trunk. Countless ways to connect.
You Upgraded to SIP. Now Your Fax Is Broken.
You migrated to VoIP and fax became a problem. Pages fail mid-transmission. Calls drop. Your IP-PBX vendor says it’s the carrier. Your carrier says it’s the device. Your device vendor says it’s the network.
They’re all partially right—and none of them are going to fix it.
Fax over SIP is hard. The T.38 protocol requires precise timing, clean UDPTL handling, and ECM error correction that most SIP providers have either disabled or never properly implemented. When your vendor says “fax over IP is unreliable,” what they mean is that their fax over IP is unreliable.
- Your carrier's T.38 "support" means T.38 pass-through to an upstream provider they don't control
- ECM is disabled by default—so corrupted pages arrive with no retransmission request
- Variable routing means the same fax number behaves differently on different days
That’s not a fax problem. That’s a carrier problem.
We Built Our Own T.38. Every Call Goes Through It.
Most SIP providers don’t actually run T.38 infrastructure—they pass your traffic to an upstream carrier who does, and that carrier’s implementation is inconsistent, shared, and beyond anyone’s control.
T38Fax is different. We collocate our media gateways inside carrier networks and handle T.38 conversion ourselves—directly to G.711 audio onto the PSTN over a single optical hop. Your equipment talks to our gateways on every call. No upstream handoff. No variable routing. No mystery failures.
Our T.38 implementation is in-house technology we’ve been building and improving for years. We understand the protocol at the level of T.30 negotiation and ECM partial-page retransmission. When something goes wrong, we can actually diagnose it.
One SIP trunk. Countless ways to deploy.
Connect However Makes Sense for Your Infrastructure
IP-PBX + ATAs
Your IP-PBX (Asterisk, FreePBX, 3CX, Cisco, Avaya) maintains a single Power-T.38 SIP trunk. Behind the PBX: analog fax machines connected via ATAs, T.38-capable fax servers, MFPs, or any combination. One trunk handles the full mix.
Direct Fax Server
A T.38-capable fax server registers directly to Power-T.38 with no intermediary PBX. Simplest possible path, lowest latency, easiest to troubleshoot. Ideal when fax is isolated from your general voice infrastructure.
ATA Direct Connect
A standard analog fax machine connected to an ATA, which registers directly to T38Fax over the internet. No PBX required. Grandstream's HT81x series is our recommended starting point for new deployments.
Other common configurations: multi-port gateways (GXW4004/4008), MFP/copier fax integration, hybrid deployments with fax servers behind a PBX, branch office setups with multiple sites on a single account.
Four Reasons to Choose T38Fax
Consistent T.38
Our T.38 stack runs on every call. We collocate media gateways inside carrier networks—your fax server talks to our gateways, not some unknown upstream provider. No variable routing, no mystery failures.
ECM Error Correction
Most carriers disable ECM to save processing power. We insist on it. Without ECM, fax pages can arrive corrupted with neither side knowing. The word "facsimile" means exact copy—that requires ECM.
Security & Compliance
SOC 2 Type II certified. HIPAA compliant. Optional VPN tunnels. We never store PHI because T.38 is real-time. When compliance asks about fax infrastructure, you'll have answers.
Premium Support
Fax industry veterans who diagnose with protocol analysis, not superstition. We understand T.30 negotiation, ECM partial page retransmission, and why your fax failed at page 47 of 200. Unlimited support included.
What Our Customers Say
"We have been using T38Fax for 18 months now. We have six locations in three western states, all 24hr healthcare facilities with critical needs in terms of faxing. After several years, we eliminated virtually every problem we had by deploying T38Fax. These guys have a powerhouse solution, rock solid, always up, that plays wonderfully with our PBX. Our faxes now are more stable than they were with POTS lines."
— Tyson Frantz, Owner, Guardian Angel Homes"We use T38Fax for over 200 of our clients and they work flawlessly. The ease of setup and maintenance is great. Their technical staff is always very fast and knowledgeable, and anything regarding porting of numbers or ordering new lines is fast and easy."
— Chad Snowdy, Network Engineer, Data SolutionsIf It Speaks T.38, It Works With Us
In theory, any T.38-capable device should work. In practice, device quirks matter—which is why we maintain a full Compatibility List with tested configurations and setup guides for everything we’ve certified.
ATAs & Gateways
- Grandstream HT801, HT802, HT812, HT814, HT818
- Grandstream GXW4004, GXW4008
- Cisco ATA 191-MPP, ATA 192-MPP
- AudioCodes MediaPack 1xx
- Patton SmartNode
IP-PBXs & Softswitches
- Asterisk / FreePBX
- FreeSWITCH / FusionPBX
- 3CX
- Cisco CUCM
- Avaya
- Grandstream UCM Series
Fax Servers
- OpenText RightFax
- HylaFAX Enterprise
- GFI FaxMaker
- XMedius
- Biscom
Not on the list? If your device supports T.38, bring it to our free trial. Our support team has seen most of it before—and if they haven’t, they want to.
Running RightFax, HylaFAX, or GFI FaxMaker? See our enterprise fax server page for deep integration details, SR140 certification, and channel sizing guidance.
Enterprise Fax ServersProviding fax service to your customers? See our Voice Service Providers page for wholesale T.38 offload, wholesale pricing, and reseller options.
Voice Service ProvidersFrequently Asked Questions
-
Yes. Grandstream ATAs—including the HT801, HT802, HT812, HT814, HT818, and the GXW4004/4008 gateways—are fully certified and among our most widely deployed devices. Configuration guides for each model are available in our Knowledge Base.
-
G.711 fax transmits analog fax tones encoded as audio—it works over short, clean network paths but degrades quickly with any packet loss or jitter. T.38 converts fax tones into a purpose-built data protocol (UDPTL) that includes redundancy, making it far more resilient over real-world WAN connections. Most SIP providers attempt G.711 passthrough and call it ‘T.38 support.’ It isn’t. Power-T.38 is a native T.38 implementation with ECM error correction always enabled.
-
An analog fax machine needs an ATA (Analog Telephone Adapter) to speak SIP. If you’re already running an IP-PBX, you may already have one. If you’re starting from scratch, we recommend Grandstream’s HT81x series for single-site deployments—they’re affordable, reliable, and well-documented. T.38-capable fax servers and IP-PBXs can connect to us directly with no additional hardware. See our full Compatibility List for certified devices.
-
Yes. T38Fax is HIPAA compliant and SOC 2 Type II certified. Because T.38 is a real-time protocol, PHI is never stored in transit on our infrastructure. We also offer optional IPSec VPN tunnels for organizations requiring encrypted transport between their network and ours. See our Security & Compliance page for full details.
-
Pricing is usage-based with no activation fees, no minimum term, and no volume commitments. Automatic discounts begin at 10,000 minutes per month. All accounts start with a 30-day free trial that includes $25 in calling credit and unlimited technical support. See Pricing for current rates.