Faxing without a phone line, after the copper goes
A fax machine needs an analogue line, and those are being switched off country by country. The number can outlive the line — the machine usually cannot.
Fax machines were designed for a network that is being dismantled. Analogue phone lines are retiring across every market we sell in, on national timetables, and when the copper goes the machine plugged into it stops working. The number does not have to go with it.
Why the machine stops and the number does not
A fax machine is a modem. It converts a page into sound and expects an analogue line to carry that sound intact, unaltered, end to end. A modern network does not carry sound — it carries compressed audio optimised for speech, and the compression that makes a voice sound fine turns modem tones into noise.
The number, meanwhile, is just an entry in a database. It can be pointed at anything, including software that speaks the protocol correctly — see how receiving a fax online works.
Why plugging the machine into the router usually fails
Most routers have a socket for an analogue phone, and the obvious move is to plug the fax machine into it. It works sometimes, badly, and here is what determines which:
- The codec. Fax needs uncompressed G.711 end to end. Anything compressed mangles the tones. You do not control which codec the far end's provider uses.
- Jitter. A voice call tolerates packets arriving late; a modem does not. A few milliseconds of variation drops the page.
- Echo cancellation, which improves speech and destroys modem handshakes.
- T.38, which exists exactly for this and helps a great deal — when both ends support it, which is not something you can check before dialling.
The symptom that wastes the most time
Fax over a router usually works for a one-page test and fails on the ten-page document that matters. Short faxes finish before jitter accumulates. If your test was one page, you have not tested it.
What actually works
- Move the number, keep the machine unplugged. The number ports; the pages arrive as files. Nothing at your end depends on a line existing. Keeping your existing number covers what that takes.
- Keep a dedicated analogue line, where a regulator or a counterparty genuinely requires a physical device. Increasingly expensive and, in several countries, no longer purchasable.
- Fax over your VoIP provider, if they support T.38 and you accept that reliability depends on the far end too.
What the recipient sees
Nothing different. They dial a fax number, hear a fax tone, get a transmission report. That matters, because the reason you still need to fax is almost always that a clinic, court or insurer requires it — and their requirement is about the number, not about what answers it.