Phone Considerations

Your choice of phone service providers can have a significant impact on your ability to fax reliably. The following information applies to all faxing; including fax machines, fax software, fax cards, multi-function printer devices, etc.

There are important considerations and caveats when choosing your phone service provider when your business requires faxing. At the end of this FAQ, we provide some top North American phone service providers and caveats for using their services for faxing. To skip the details and go to the summary, please click here.

With the integration of digital phone and internet services, including ADSL, DSL, VOIP and Broadband, signal compression has become a common practice. There are two types of compression – “Lossy” and “Lossless”. Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. Lossy data compression, however, only allows constructing an approximation of the original data in exchange for better compression rates. As far as faxing is concerned, “Lossy Data Compression” creates problems when faxing. Compressing data allows more information to be sent over less bandwidth at faster speeds. The problem in compressing data when faxing (using lossy data compression), however, is that relevant fax data will be lost. Fax signals cannot be compressed with lossy compression as relevant data will be lost (unlike voice signals), as all fax data is considered essential. For this reason, special care must be taken when choosing and configuring a non-analog phone service to ensure no fax data is lost. With G.729 voice compression, certain portions of voice data can be omitted with minimal loss of clarity (between 300 Hz – 3400 Hz). With G.729 fax compression, however, relevant data is lost, and fax integrity is compromised.

When choosing a digital phone service on which you intend to fax, you must take steps to accommodate and ensure your faxing conditions are optimized. Faxes sent over ADSL, DSL and VOIP will fail consistently – unless certain steps are first taken to improve the reliability. When using these digital services without accommodations, faxes may appear to completely send, yet the receiving party may only receive a partial or incomplete fax. The fax sender, if operating on a DSL or VOIP service that was incorrectly setup, may get confirmations of sent faxes that were not actually sent. Reviewing phone services in advance will allow you to integrate faxing and avoid common pitfalls brought on by the lure of a reduced phone bill.

Following are some of the common phone services available today along with the necessary steps to ensure your fax works reliably. If you need fax, your optimal choice with the highest reliability will be an analog phone service.

Phone Service Types Overview

  1. Analog: Traditional phone lines guarantee the highest quality and reliability for faxing. Traditionally called POTS (for plain old telephone service), analog phone lines get along well with fax machines and fax software because fax was designed for analog service. If you experience poor analog phone line quality, it may necessitate you install an analog phone filter. Remove any splitters from the line. Do not share a fax machine and fax software on a line splitter. The signal will be reduced (attenuated) and the results may be unreadable. Below (on the left), is a USB modem connected to an analog phone line.
    USB Modem
  2. DSL: DSL phone services are less reliable for faxing than analog faxing and, as a rule, will require a DSL line filter  to improve reliability. DSL line filters can be obtained for $5 – $20. To learn more about DSL filters, please visit here. DSL FilterPlease notice the DSL filter (see picture above) is plugged directly into the incoming phone line and, on the other side, the analog RJ-11 phone cable is connected. With ADSL lines, fax signals are sent via a regular telephone service, but you will need an ADSL filter to block the ADSL from reaching the fax machine. To learn more about ADSL Filters, please visit here
  3. VOIP: VOIP phone service can create major problems for fax machines and fax software. Most notably are the G.729 Codecs used for compressing voice signals. If VOIP is not your only solution, then we suggestion opting for Option 1, an analog line. If you are stuck with VOIP, here are some suggestions: A. When using VOIP, ensure the G.711 codec is used and the G.729 codec is not. This is likely a setup the VOIP installer can perform upon request. B. Lower the Baud rate to 2400 – 4800. The lower the speed, the higher the reliability. C. Remove line splitters or other devices. D. Lastly, try placing a DSL filter in reverse position between the ATA (Analog Terminal Adapter) and the Fax modem or fax machine. The ATA connects the fax modem or fax to a VOIP network via an RJ11 jack.
  4. Majic Jack: We do not recommend this for fax service. The failure rate is unacceptably high.

Phone Service Providers and their primary type of phone service (listed alphabetically):

  1. AT&T: AT&T commonly uses ADSL or DSL. We suggest after confirming this, you invest in an appropriate filter (DSL or ADSL). Alternatively, and we recommend this, AT&T will commonly accomodate a hybrid installation and provide you with a direct analog connection for your FAX Server upon request.
  2. Comcast: Comcast commonly uses ADSL or DSL. We suggest after confirming this, you  invest in an appropriate filter (DSL or ADSL). Alternatively, we recommend you ask Comcast to accomodate install a direct analog line for your FAX Server upon request (a hybrid installation).
  3. Time Warner: Time-Warner offers a “VOIP telephone service” (known as Voice Over IP).  VOIP phone systems are notoriously hostile to faxing as they were designed for voice. The best results for faxing with a VOIP, is to lower the baud rate to 9600 baud, but do not expect 100% success. To accomodate VOIP Services, 4-Sight FAX uses HARDWARE flow control and ERROR CORRECTION capability is turned off. If this service is installed, make sure your VOIP connection uses the G.711 Codec to avoid compression.
Thanks to Wikipedia for portions of the above content.