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Why Does My Fax Machine Not Work on My VoIP Phone Line?

Fax MAchine

If you need to send out a fax immediately, I would just sign up for an online fax service like RingCentral Fax.

RingCentral Fax is a computer fax service that offers a 30 day free trial and then its $17.99/mo. If you want to cancel, Ringcentral also provides a risk-free 30 day money-back guarantee.

One of the biggest sources of confusion about faxing from a computer involves why you can’t use a VoIP phone line.

In all of the tutorials about how to fax from a computer, you’ll see that you need an active landline phone line, and most tutorials will specifically tell you not to use a VoIP line because it won’t work.

Why can’t you connect your fax machine to the phone network using a VoIP phone line?

The shower answer is that it just doesn’t work that way. Fax machines cannot and will not work over VoIP lines.

Of course, there are always exceptions. If you look online, you’ll find that some users with some VoIP providers have found a way to make faxing work over a VoIP line. Nevertheless, few of these methods are reliable enough to recommend to the average user.

Why It Doesn’t Work

Do you want to know the long answer about why VoIP doesn’t accept fax data?


The long answer is that the two are incompatible with each other.

You see, VoIP devices digitize and compress analog voice communication in a way that’s optimized for voice audio and not fax signaling.

Humans communicate with complex words, sentences, and sounds. Machines – like fax machines – communicate with their own complex sounds in the forms of high pitched beeps.

Understandably, VoIP is not prepared to handle these complex machine sounds.

VoIP lines take the sound of someone’s voice then digitally compress it for transmission over the internet. Your voice is transmitted into the device in the form of sound waves. VoIP lines transform those sound waves into binary computer language (1s and 0s). Once that binary data reaches the other end, your recipient’s VoIP system converts the computer language back into sound waves that you can understand.

Fax machines are fundamentally different. A fax machine takes an image of a document and turns that image into binary computer language (1s and 0s). Then, that computer language is turned into a sound wave that can be transmitted through your existing phone lines.

Why does fax data need to be transformed into a sound wave? Because you’re sending it through an audio-based phone line.

Once your fax reaches your recipient’s fax machine, that receiving machine translates the sound wave back into computer language, and then translates it once again into an image.

The Problem Lies in the way VoIP Converts Audio

If you try to send a fax through a VoIP connection, the audio file from that fax will get scrambled and distorted.

The way that a VoIP signal converts audio into computer language distorts the signal from the fax machine, which means that it cannot be understood by the receiving machine.

In layman’s terms, there are too many steps involved in sending a fax for VoIP to accurately handle faxing. Each step leads to a quality loss problem until eventually, your fax is just a meaningless stream of data being sent through VoIP.

How to Fax Over a VoIP Phone Line

Fax Over VoIP

Remember up above when I said that there were some ways to fax over a VoIP phone line? It’s true! With a little bit of technical workaround, you too can fax over a VoIP phone line.

Some VoIP providers even provide FAQs or tutorials that promise to make it easier to fax over a phone line.

Here are some frequently-recommended tips that promise to help anyone fax over a VoIP line:

  • Lower the transmission rate (also known as the baud rate) of the fax machine to the lowest possible setting. This forces the fax machine to transmit data at an artificially slow pace. It also significantly reduces the clarity of the fax. However, stretching out the transmission can make the signal less susceptible to getting scrambled over VoIP.
  • Enable Quality of Service (QoS) in your router. QoS is a system that prioritizes a certain type of network traffic over other types of network traffic. Enabling QoS on your router for your VoIP service will prioritize VoIP traffic before all other traffic. So if your internet connection gets slow, then you’ll still be able to transmit voice traffic through the router. In some cases, your faxes get scrambled through VoIP because your VoIP data is not prioritized on the network.
  • Buy an Analog Telephony Adapter (ATA) that supports T38, which is the protocol designed to allow faxes to travel over VoIP
  • Consider signing up for online faxing or similar services, which we’ll explain in the next section

Other Ways to Fax that Don’t Require a Phone Line

Not all faxing methods require a phone line. Today, a wide range of online fax providers have made it easy to cut the cord on your phone bill and send faxes exclusively over an internet connection.

With online faxing, you can get your own online fax number or port an existing fax number to the service.

If you don’t want to sign up for online faxing, then you may need to buy a phone line from your local phone company that is used exclusively by your fax machine. Because without a complex technical solution, sending faxes through VoIP simply doesn’t work.


About Johnson Hur

After having graduated with a degree in Finance and working for a Fortune 500 company for several years, Johnson decided to follow his passion by embarking on a path to the digital world. He has over 8 years of experience with large companies setting marketing strategy.

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