Inexpensive long-distance telephone rates are now common. In the past, before Voice over Internet Protocol (VoIP) services became widespread and the Public Switched Telephone Network (PSTN) was the primary telecommunications network, most US consumers anticipated long-distance toll charges of around 10 cents per minute. However, over the past decade, both residential and business consumers have largely shifted to more affordable long-distance carrier services, often costing 5 cents per minute or less. This cost reduction from 10 to 5 cents per minute is primarily fueled by telecommunications competition leveraging VoIP services.
Although the move towards more affordable VoIP services may benefit voice communications, it presents challenges for fax users. The difficulties associated with using VoIP for fax communications are explained well in our blog post “The Challenges of Subpar Audio Quality”. Consequently, fax users who are diligent about their operations should choose services that are specifically engineered and tested for fax transmission.
Since introducing the Centralis Health hMessage and hFax, we often get asked by potential customers why the outbound pricing is $0.07 cents per-page when they can readily find $0.05 cent per-minute long-distance for their own business use. The answer is that ultimately the per page rate is actually less expensive than the per minute rate – when used for fax.
We know you are wondering; how can this be?
Understand that fax data consists mainly of image data and secondarily of handshaking data. Any flaws in the audio quality of the fax call directly affect the data received. Issues with image data can lead to distortions in the fax or, more commonly, longer transmission times due to error correction processes that retransmit parts of the image that didn’t transmit correctly. Problems with handshaking data are even more critical. Inaccurate handshaking signals are inconsistently handled by different fax devices, which usually have only a small margin for error. This tolerance often runs out quickly, leading to a protocol error and fax failure.
In cases of flawless call audio quality, there is no data loss, no need for retransmissions, and no protocol errors. However, since we cannot always control the remote endpoints or the carriers in between, achieving perfect conditions is rarely possible. In our “Assessing Line Audio Quality,” Centralis Health defines a “good” line as one with a maximum retransmission rate of 2% and no protocol failures. In comparison, a typical fax retransmission rate with a 5 cent per-minute VoIP long-distance service is often around 10%, accompanied by a similar rate of protocol errors.
Next, we need to do some calculations, but first, it’s important to note that different fax sending software handle protocol failures differently when retrying a fax. For example, HylaFAX typically starts re-sending from the first unsent page, while Microsoft Fax (also known as Windows Fax Service or Windows Fax and Scan) will resend the entire fax starting from the first page. For simplicity, we’ll refer to these two approaches as “HylaFAX” and “MS Fax.”
For our calculations, we’ll assume that the average fax is two pages long, with each page taking 40 seconds to transmit under ideal conditions without any retransmissions or errors. (Of course, these assumptions can vary significantly depending on specific use cases.)
Due to the handshaking protocol involved in retransmitting image data, retransmitting 10% of the data does not simply add 10% to the total transmission time. In fact, the additional protocol communication time can often equal or exceed the time needed to retransmit the data itself. Therefore, we’ll estimate that transmission time increases by 20% on the 5 cent per-minute service
If 10% of fax attempts fail due to protocol issues, additional time will be required to retransmit the pages of the fax image data that were not fully transmitted before the failure. For the HylaFAX scenario, this will add 20 seconds (equivalent to half a page, on average) for every ten faxes. Given that each page of the average two-page fax takes 40 seconds to transmit, this adds 20 seconds for every 800 seconds of transmission time, resulting in an additional 3%. In contrast, for the MS Fax scenario, retransmitting the partially-transmitted fax will add 40 seconds (about half of the 2-page fax) for every 800 seconds, which amounts to an additional 5%.
Therefore, combining the 20% increase in transmission time with the additional 3% or 5% results in a total increase of 23% or 25%, respectively. For simplicity, we’ll use the 25% figure.
This 25% increase in transmission time also indicates a reduction in throughput capacity. A decrease in capacity means more lines are needed to handle the same volume of traffic. For example, if a business fax line is available 8 hours a day for 5 days a week and costs $50 per month for the service subscription, this equates to 3 cents per minute. With a 25% reduction in capacity, the effective cost rises to nearly 5 cents per minute, resulting in a 2-cent per-minute difference due to poor call audio quality.
Furthermore, this capacity reduction affects both ends of the call. The receiver also experiences diminished capacity due to the sender’s use of low-quality phone services. Thus, the total opportunity cost is 2 cents per minute for the sender and 2 cents per minute for the receiver, amounting to a total of 4 cents per minute.
Let’s summarize the findings. A 25% increase on a 5 cents per-minute rate results in a rate of over 6 cents per minute. Adding the 4 cents per minute in opportunity costs brings the total to more than 10 cents per minute. This rate exceeds that of higher-quality services and comes with additional complications. You might consider assigning a monetary value to this added difficulty to conclude that “affordable” long-distance services with poor fax audio quality do not offer any real savings.