A fax machine scans a document, converts it into an audio signal, and sends it over a phone line to a receiving machine that prints it instantly. Here is exactly how fax machines work, what their parts do, and why millions still use them today.
Frequently Asked Questions
What does a fax machine do?
A fax machine scans a physical document, converts the image into audio-frequency tones, and transmits those tones over a telephone line to a receiving fax machine, which decodes them and prints a paper copy. The whole process typically takes 30 seconds to a few minutes per page.
Do you need a phone line to use a fax machine?
Traditional fax machines require a phone line. However, modern online fax services like [mFax](https://mfax.to) work without any phone line or hardware — you send and receive faxes directly from your smartphone or computer.
Is a fax machine the same as a scanner?
No. A scanner only captures a digital image of a document and saves it to a computer. A fax machine scans the document AND transmits it over a phone line to a remote printer at the same time. A fax machine contains a scanner as one of its components, but it does much more.
Why are fax machines still used today?
Fax transmissions travel over dedicated phone lines, making them harder to intercept than email. They also create a verifiable delivery record. For these reasons, healthcare, legal, and government sectors — including the IRS — still rely on faxing for sensitive documents.
What is the difference between a fax machine and online fax?
A physical fax machine requires phone line hardware and thermal paper. Online fax services convert your document into a fax signal digitally and deliver it over the same phone infrastructure — no machine, no cables, no paper. You send from any device in seconds. See our [guide to the best online fax services](/blog/best-online-fax-services/).