How Fax Machines Work (Hint: It's Not Teleportation)
Thursday, April 15, 2021
There’s a funny scene about technology in the Fox TV crime drama Gang Related. The lieutenant of a gang task force suspects one of his cops is leaking information to the gang leaders, so he calls a meeting with the team and demands they all hand over their devices. Then he says, “Until everybody’s equipment has been checked, we will be on communications lock down—meaning no cell phones, no land lines, no internet, and no fax.” At which point, one cop whispers to another, “Wait, we still have fax?”
Yes, for better or worse, we still have fax.
The fact that today you might still have a need to send a fax is amazing when you consider that faxing has been around for literally 150 years, easily making it the oldest technology you have in your office. (Unless you do your bookkeeping with an abacus.)
Granted, you may not even know how to use a fax machine. And today, you can use modernized versions of this 19th century communication technology—you can send a fax online, fax by email, and even fax on your phone with a mobile fax app. But you’ve got to admit: Fax has proven that it has staying power.
So it’s probably worth learning how the underlying technology works, right? It’s actually pretty cool.
Table of Contents
- How a Fax Machine Reads Your Fax Document
- How a Fax Machine Sends Your Fax
- Your Faxing Doesn’t Have to Work This Way
How a Fax Machine Reads Your Fax Document
Before your fax machine can transmit your paper document to your recipient’s fax machine, it first needs to “see” the document and record what’s on it.
We use the term “see” because, when you feed your document into a fax machine, it uses a built-in photo sensor to view the page as a series of tiny squares (maybe just a hundredth of an inch each), and then records each square as either black or white. The reason older fax machines often used a rotating drum for paper-feeding was so the machine could record a single line’s worth of these tiny squares at a time, then rotate to the next line.
Once the fax machine has recorded a page’s contents, it converts each of the squares into a sequence of audio tones, using different tones to signify that a square is either white or black. (Cool, huh?)
With the page’s info recorded on your fax machine, now it’s ready to transmit.
How a Fax Machine Sends Your Fax
To send your fax, your fax machine (in most cases) actually uses the plain-old telephone network. When you dial your recipient’s fax number on the machine’s keypad, and the two machines connect, your machine starts sending those audio tones over phone lines.
This is what you’re hearing as your fax machine makes those horrible screeching and beeping noises. It’s screaming to your recipient’s fax machine, telling it what to print: “Black square! White square! Black! Black! White, white, white! Black, white, black!”
In other words, you’ve probably listened to many of your faxes translated into “telephone-ese” without ever realizing it.
Your Faxing Doesn’t Have to Work This Way
Technology has come a long way since the 1840s, when the first fax device was invented—and since the 1980s, when the analog fax machines we described above went into widespread use in business.
So you can keep faxing like it’s 1989, standing over your desktop fax machine, waiting for it to finish screaming, “White square! Black square!”
Or you can ditch the machine altogether—and start faxing online, from anywhere.