This page is about a how a fax machine “works” (the technology behind it).
For how to use (and set up) a fax machine (the actual operation of it) see our page on “how to set up a fax machine.”
The ability to send an image over a wire predates Alexander Graham Bell’s invention of the telephone. Today’s fax machines work with many of the same concepts as those earlier inventions, but with today’s technology.
Table of Contents
- How faxes communicate
- A fax transmission example
- Today’s fax technology
- The fax machine of the late 20th century
- Pre 1960s fax machines – the history of fax
- More “how a fax machine works” resources
- More “how to fax” articles
All fax machines and fax transmissions revolve around the same basic concept – they scan a document, transfer the image of that document over to a signal, then send that signal to another fax machine that decodes the signal and prints the document back out.
Early fax machines simply worked on two tones – one for there being an image on a certain point on the page, and one for not being an image on a certain point on a page. This would result in either a black dot or white dot being transmitted over to the other machine.
Just like a computer screen or LCD display is made up of many tiny dots to put a picture together, a fax records that information to send it back in much the same way.
Today’s fax machines are much close to a scanner hardwired into a printer than they are the models from 10-20 years ago. Digital technology has made for a much more accurate picture as well as faster and compressible transmissions.
A fax transmission works in a number of steps – the fax machines handshake, transmit their message, and the send confirmation.
Step 1 – the Handshake
The handshake is the first part of a fax communication.
When a fax is being sent, the sending machine waits for the line to pick up and then starts sending a series of beeps.
These beeps signify that the machine is requesting to send a fax. The sending fax machine is essentially saying “Hey! I’m a fax machine! I’m looking for another fax machine! Is there one there?”
If the machine on the other end is also a fax, that fax will answer the beep with its own signal. At this point the receiving fax machine is saying “Hey you’re a fax? Guess What? I’m a fax too!” And both machines now know that they’ve each made a friend.
Once both machines have acknowledge each other, they send information back and forth about them (just like two people getting to know each other). This information is along the lines of whether they are analog or digital faxes, as well as what compression formats they speak.
Once the two fax machines understand what the other is capable of, they decide on a format to send with, and then start their transmission.
Step 2 – Transmission of Messages
After the handshake has occurred, the sending fax will send the message through to the receiving fax.
As both machines know that they speak the same language, they’re able to send the messages through in a format that they know the other machine knows.
Step 3 – Confirmation of Message Reception
Once the message has been sent, the final step is the confirmation of the message being received. The receiving fax machine will send a confirmation notice, that the sending fax machine can now print out.
Today’s version of fax has changed very much from the power machines of the 1980s and 90s.
The majority of fax transmissions now happen through online fax services, fax servers, or fax boards that are part of larger multifunction machines.
Most of today’s fax machines consist of three parts:
- A scanner
- A printer
- A fax modem (phone line)
When sending a fax, the scanner and fax modem work together – the scanner by capturing the document and turning it into a digital signal, and the fax modem by sending that signal over the phone line.
When receiving a fax, the printer and the fax modem work together – the fax modem by collecting the digital signal that arrives over the phone line, and the printer by turning that digital information into a printed piece of paper.
The benefit of this approach is that fax technology can work with a number of printing technologies (ink and toner, across a number of different brands), or a combination of machines (scanning in one area, printing in another, and transmitting faxes through either machine or a computer’s fax server).
Fax options on a multifunction unit (printer / scanner / copier / fax)
With a fax machine is part of a unit that also prints, scans, and/or copies, it is called a “multifunction product” “multifunction printer” or “MFP”.
When a fax is present on an MFP, the fax modem in the fax part of the machine works with the scanner and the printer portion of the MFP to scan or print the fax.
Fax Servers and Online Fax Services
The largest shift in fax technology has come from a shift towards fax servers and online fax services.
An online fax service is a system that provides users the ability to fax without having a fax machine or a phone line. Accessed through the internet, a fax service takes care of the technical details while the user has access to an interface that is very much like web-based email programs such as hotmail or gmail. Online fax services also have features such as being able to send and receive faxes through email.
A fax server is very much like an online fax service, however it is typically used in an enterprise level system (run by an organization’s IT department) with many users sharing the resource.
Fax machines hit their peak in the decades of the 1980s and 1990s.
A fixture in every office, home use of the fax machine was also widespread.
Late 20th century fax machines pre-dated the multifunction unit – they were standalone devices and worked on technology closer to that of traditional photocopiers than of today’s printers.
Prior to the introduction of the “modern” fax machine around the mid 1960s, fax was in place in different formats for almost a century.
A service with the ability to electronically transmit an image over distance was in place in France around the time that the US Civil War was ending (at the time Alexander Graham Bell, the inventor of the telephone, would not even have been 20).
First as a connection between two synchronized clocks, and later using pieces of chemically impregnated paper, telegraph lines were used in the first true example of a fax transmission.
Between the 1860s and 1960s, fascimile transmissions went through a number of changes, but remained an important part of communications in business and government – from sending maps during wartime to other functions where courier would be too slow.
For more on fax machines in the Pre-1960s era, see our page on “The History of Fax”
- Explain that stuff – How does a fax machine work
- How Stuff Works – How fax machines work
- Wikipedia – Fax
- The Secret life of Machines – the Fax Machine
- How to Fax From a Computer – How To’s and Instructions for Faxing from a Computer
- Windows 7 Fax – How to setup and operate faxing on Windows 7
- Windows XP Fax – How to setup and operate faxing on Windows XP
- How to Fix a Paper Jam in a Fax Machine – Prevention and Maintenance for Paper Jams
- How to Fax Internationally – International Dialing Codes and Calling Methods
- How to Get a Fax Number – Finding Fax Numbers for Local and Toll Free Services
- How to Send a Fax – Methods for Faxing, from Online and Internet Faxing to Fax Machines and Computer Faxing
- How to Use a Fax Machine – Including Configuration, Sending, Receiving, and Troubleshooting
- Where Can I Send a Fax? – How to Find Places and Methods that Can Send Faxes