Fax is older than email, yet millions still use it every day. Here's exactly how fax technology works — from analog phone signals to modern online fax — and why it's still the preferred method for legal, medical, and government documents.
Frequently Asked Questions
How does a fax machine work?
A fax machine scans a document into pixels, converts those pixels into audio tones, and sends them over a telephone line. The receiving fax machine decodes the tones back into pixels and prints the document. The entire process takes 30 seconds to a few minutes per page.
How is fax different from email?
Fax transmits a document as an image over a phone line, creating a time-stamped delivery record. Email sends data over the internet, which offers no built-in legal delivery proof. For this reason, courts, the IRS, and healthcare providers still require fax for official document submission.
How does online fax work?
Online fax services like mFax convert your digital document into a fax signal and deliver it over phone infrastructure without you needing any hardware. You upload a PDF on your phone or computer, enter a fax number, and the service handles the rest — including a delivery confirmation.
Why does a fax machine make that screeching sound?
That noise is the handshake negotiation — two fax machines exchanging tones to agree on transmission speed, compression, and error correction before sending any document data. It typically lasts 3–5 seconds.
Is faxing still secure?
Traditional fax over a dedicated phone line is considered more tamper-resistant than email because it does not pass through internet servers. Modern online fax services add TLS encryption during transmission, making them equally secure. For HIPAA-sensitive documents, services like mFax Business provide full compliance with encryption, BAA agreements, and audit logs.