A fax machine scans a document into pixels, converts those pixels into audio tones, and sends them over a telephone line — where a second machine reassembles and prints them. Here's exactly how it works, what's inside the machine, and why millions still use fax today.
Frequently Asked Questions
How does a fax machine work step by step?
A fax machine scans your document into a grid of black-and-white pixels, compresses the data, converts it into audio tones, and sends those tones over a telephone line. The receiving machine decodes the tones back into pixels and prints the page. The entire process typically takes 30 seconds to 2 minutes per page.
What are the main components of a fax machine?
A fax machine contains three core systems: a scanner (reads the document), a modem (converts data into phone-line tones and back), and a printer (reproduces the received document). It also includes a telephone handset connection, a document feeder, and control electronics.
Why does a fax machine make a screeching sound?
The screeching noise is the T.30 handshake — the two fax machines exchanging tones to negotiate transmission speed, resolution, and error-correction settings before any document data is sent. It lasts 3–5 seconds and is a normal part of every fax call.
What is the difference between a thermal fax and a plain-paper fax?
Thermal fax machines print on special heat-sensitive paper that fades over time and cannot be highlighted. Plain-paper fax machines (laser or inkjet) print on regular paper, producing durable, permanent copies. Most modern offices use plain-paper multifunction printers that include fax functionality.
What is a fax machine used for?
A fax machine is used to send an exact image of a printed document to another fax machine over a phone line. It is most common in healthcare, legal, financial, and government settings, where a faxed document serves as a legally recognized, tamper-resistant record of delivery that email cannot reliably match.
Do fax machines still work in 2026?
Yes. The global phone network still carries fax traffic, and an estimated 17 billion fax pages are sent every year — mostly in healthcare, legal, and government. The main change is that most faxing now happens through online fax services rather than physical machines, though the two are fully compatible.
Do I need a fax machine to send a fax today?
No. Online fax services like mFax let you send and receive faxes from your phone or computer — no machine, phone line, or paper required. You upload a document, enter a fax number, and the service transmits it over the same phone infrastructure as a physical machine. The recipient cannot tell the difference.