How Does A Fax Work?

The fax machines have been around for more than 150 years now, as one of the oldest technologies to send and receive documents.

Even today, fax machines are still relevant, and people rely on faxing to send important files because they are one of the most reliable and secure methods of communication. 

However, have you ever wondered how a fax work and what is the technology behind this 19th-century communication technology? If yes, this article is for you. Let’s find out together!


Key Takeaways

  • Most fax machines use the old telephone network to send the fax.
  • The fax transmission happens in three steps- The handshake, transmission of the document, and message confirmation.
  • A fax machine has three main components- A scanner, a printer, and a phone line or a modem.

What is a Fax Machine?

What is a Fax Machine

A fax machine scans text and images from a document and transmits the exact thing on the receiver’s paper. A fax machine produces the exact copies of your documents.

Instead of sending pictures of your documents to the sender, you can send identical physical documents by using a printer. To use a fax machine, you need access to the following:

  • Fax machine
  • A telephone line
  • Ink or toner paper 1

History of the Fax Machine

How Does A Fax Machine Reads The Document?


Before sending the fax, the fax machines split up the document into a grid of squares, similar to pixels, to see what it says.

Here’s how it works:

  • When you feed the document into the fax machine, the built-in photo sensor views the paper as a series of tiny squares and records each square as either black or white. 
  • It records the page’s info and converts each of the squares into a sequence of audio tones with different tones to signify that the square is either black or white and then transmits it. 2 

Read: How To Receive A Fax Without A Fax Machine?

Also Read: How To Fax Over The Internet?

How Early Fax Machines Worked?

The early fax machines used to work through telegraph lines that transmitted images and texts using long and short codes.

A sensor located inside the sender’s fax machine would read each line and transmit it to the receiver’s machine.

Then the receiver’s machine would print the information available on the paper one by one. 3

How Does A Fax Machine Send A Fax? 

Most fax machines use the old telephone network to send the fax.

When you dial the recipient’s fax number, your fax machine tries to establish a connection with the recipient’s fax machine to send those audio tones over phone lines, and that’s why you hear those beeps and screeching noises.

The receiving fax machine then accepts the message, decode it, and prints it out. 

How Does A Fax Transmission Work?  


Modern fax machines use the same principle as facsimile transmission. The majority of fax transmission occurs through online fax services, fax boards, or fax servers.

Today, fax machines have three main components: 

  • A Scanner
  • Printer
  • A phone line or a modem

Once you scan a document, the fax machine scanner automatically scans and converts it into a digital signal sent through the phone line to another fax machine that decodes the signal and prints the document.

Let’s take a look at the three basic steps of fax transmission: 

  1. The Handshake 

Before sending the document, the first step is to confirm that the recipient’s machine is ready to accept the document transfer.

This process is known as a handshake, which sounds like a dial tone, and signifies the machine’s request to send a fax. 

Once the receiving fax machine responds with a beep, it shows it is also a fax machine, and you can easily transmit information back and forth.

  1. Transmission of the Document 

After the handshake, the sending fax machine will send the fax to the recipient’s fax machine.

If both fax machines use the same language, they can easily send the messages in a format that the other machine knows. 

  1. The Confirmation Message 

The third and final step is the confirmation notice that your fax has been received on the other side.

Once your fax transmits successfully, the receiving machine will send you a confirmation message that you can then print out. 4

Read: 10 Best Fax Apps For Android

Wrapping Up

So in this article on how does a Fax work, we shared the history of fax machines with you, how they send and receive faxes, what’s the process behind this and more. We hope you found this useful. 


Is the fax sent when you recieve no answer?

“No answer” to a fax machine can mean two things. Either the fax machines failed to connect, or there is no fax machine at the number entered. 

How to check if a fax went through?

If your fax gets sent successfully, it should print a confirmation page containing the summary of the fax, such as the recipient’s number, date, time, number of pages sent, etc.

How long does a fax take to get sent?

A fax may take 30 seconds to a minute to successfully send each page. Because fax machines use cellular or landline networks, the transmission is slower as compared to emails or messaging. 

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