POTS Replacement for Fax
Keep Your Fax Machines When the Copper Goes
Your copper fax lines are being retired. Keep your fax machines and your fax numbers with a certified adapter and a SIP trunk built for fax.
Your Fax Lines Are on the Retirement List
Carriers have been shutting off copper phone service for years, but the pace quickened in 2026 thanks to the FCC’s Network and Services Modernization Order, which made it easier for carriers to retire their copper lines. AT&T can begin disconnecting nearly 90,000 customers in 18 states on or after November 15, 2026, and Verizon, Frontier, and Lumen each have their own filings, too. When customers receive these notices, the window to act is often very short.
Fax lines are the ones offices forget. Alarm and elevator lines get flagged during a copper retirement because they’re life-safety equipment. The fax machine in the back office keeps working right up to the day the line goes dead, and the number on your referral forms and letterhead goes with it.
The carrier’s replacement line rarely helps. Most replacement VoIP services carry fax as audio over a voice codec, which works on a clean connection and fails when it isn’t. Faxes may begin to fail at random partway through sending, calls may connect but fail to get any pages through at all, or the pages that do get through may be distorted and unreadable. The only advice these carriers will give you is to slow down the transmission speed and retry. You will likely become very superstitious as you chase these random failures, and they’re not your fault.
Keep the Fax Machine. Keep the Number.
You don’t need new fax machines or a new fax number. A certified analog telephone adapter (ATA), meaning one we’ve tested with Power-T.38 and documented in our knowledge base, connects each fax machine to your network, and a Power-T.38 SIP trunk carries the fax over the internet using T.38, the standard built for fax over IP. Your fax numbers port to T38Fax, so senders keep using the same numbers they always have.
1. Connect a certified ATA. Plug the ATA into your network and your fax machine, then follow the step-by-step setup guide for your model. Our support team works through it with you if anything doesn’t behave.
2. Test first, then port. Send and receive test faxes using a local number you get from us when you sign up. Once faxes work in both directions, port your fax numbers to us. Porting is free, and most orders complete within 6 to 9 business days. Keep the copper lines active until the port is complete.
3. Cut over. When the port completes, quickly test again in both directions, then say goodbye to the copper lines.
Three Things, and You Probably Have Two
An internet connection at each location with a fax machine. Fax uses very little bandwidth.
A certified ATA for each fax machine, or one multi-port ATA or gateway for several machines. These are the models most offices start with:
One fax machine
Two or more fax machines
The full Compatibility List covers more than 80 tested devices. Some Toshiba and Lexmark multifunction printers speak T.38 natively and don’t need an ATA at all.
Power for the ATA and router. A copper line powers itself; an ATA doesn’t. If faxing has to keep working through a power outage, put the ATA, router, and fax machine on a small battery backup (UPS).
Running a fax server instead of fax machines? RightFax, HylaFAX Enterprise, and GFI FaxMaker connect straight to a Power-T.38 SIP trunk. See Enterprise Fax Servers.
Why Not Just Take the Replacement VoIP Line?
Because it was built for voice calls. A VoIP line that passes fax as audio, or hands T.38 to an upstream carrier it doesn’t control, gives you the same intermittent failures copper never had. T38Fax runs its own T.38 stack, offers Error Correction Mode (ECM) on every call, and diagnoses failed faxes from protocol traces. What a SIP trunk needs to support fax explains what to check on any carrier, including us.
We have saved about $1,000/month using T38Fax vs traditional POTS lines for our faxes. Support has been great and it just works, after some extensive testing.
Michael Jones, IT Manager, Chautauqua-Cattaraugus Library System
Found T38Fax and set up a trunk for testing. The folks at T38Fax told me what settings to look for. Once these were set correctly, everything works great! … We are now free of land lines altogether.
Billy Lott, Safety Coordinator, Max Foote Construction
Already on VoIP and fax stopped working? Why fax fails on voice lines and IP-PBXs, and how to fix it without replacing your equipment.
Business Fax Connectivity →Checking a specific device? More than 80 tested ATAs, gateways, fax servers, and fax machines, each with a setup guide.
Compatibility List →Frequently Asked Questions
- Yes. Most fax machines keep working when they’re connected through a T.38-compatible analog telephone adapter (ATA) instead of a copper line. The ATA plugs into your network and your fax machine, converts the fax call to T.38, and sends it over a SIP trunk built for fax. Your staff use the machine exactly as before. The Compatibility List shows every ATA T38Fax has tested, each with a setup guide.
- There are three ways. You can connect your existing fax machine to an analog telephone adapter (ATA) and a T.38 SIP trunk, which keeps your machine and your number. You can connect a fax server directly to a T.38 SIP trunk. Or you can switch to a hosted cloud fax service and send from email or a web portal. The first two keep your current workflow; the third replaces it. What Is Cloud Fax? Three Models Compared explains the trade-offs.
- Yes, if you port it before the line is disconnected. Porting local and toll-free numbers to T38Fax is free, and most orders complete within 6 to 9 business days. Keep the copper line active until the port is complete. The porting guide lists the documents you’ll need.
- A copper line carries its own power, so a fax machine on copper keeps working when the building loses power. An ATA and your internet router need power and a working internet connection. If faxing has to continue through an outage, put the ATA, router, and fax machine on a battery backup (UPS).
- No. T38Fax is a fax carrier, and Power-T.38 SIP trunks are built for fax only. Alarm panels, elevator phones, and other life-safety lines need a replacement designed for them. Ask your alarm or elevator service company what they support.
- You pay a monthly fee for each SIP trunk and each fax number, plus a per-minute rate for calls. There’s no charge to port numbers. Current rates are on the Pricing page, and the 30-day free trial includes a $25 credit for testing.