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									                                               #305, 9425 -94 Ave
                               Fort Saskatchewan, AB CANADA
                                                   (780) 702-5777

       Reliable Faxing over IP using SatFax
               Fax Terminal Adapters (FTA)

                                      Shawn Lawrence
                       Chief Technology Officer (CTO)
                               Virtutone Networks Inc.

       Our FTA hardware is award winning.
               Contents                     The Problem: Faxing Over IP (FoIP)
                                            Why traditional faxing over Voice Over IP
The Problem: Faxing over IP (FoIP)      3   does not work

                                            Previous Methods
Previous Methods for Faxing over IP 3
                                            Faxing over audio streams
                                            Faxing using T.37 fax to email service
The Solution - SatFax SF7000 Series         Faxing using T.38 Fax Relay
Fax Terminal Adapters (FTA)             6   Sending images using a scanner and a PC

                                            The Solution – SatFax FTAs
Current SF7000 Series Models            8
                                            The SatFax solution bridges the gap
                                            previous Faxing Over IP solutions could
How it Works                           10   not provide and provides features not
                                            found on traditional faxing solutions.
Why the SatFax Solution Is Right for        Current SF7400 Series Models
You                                    11   An overview of the current SF7400 series
                                            models and their technical specifications.

                                            How it works
                                            Technical overview of the SatFax solution

                                            Why you need to get SatFax units part of
                                            your next Voice Over IP solution.

The Problem: Faxing over IP (FoIP)
The business world is quickly beginning to discover the progressive technical and budgetary
opportunities that come with the move to a Voice over IP (VoIP) based telephone system. The
savings in operational budgets coupled with the impressive selection of features and options
available make VoIP business telephone systems hard to ignore.

The one area that has been a challenge for all VoIP providers has been the inability to offer a
truly reliable fax solution. Most customers have been advised to leave one Telco supplied line
in place to use for the purposes of the fax machine. Some have attempted to utilize VoIP fax
solutions and alternate protocols that traditionally offered at best a 70% success rate. Due to
the unreliability of these solutions, VoIP providers have been overwhelmed with constant
complaints about their faxing problems and put VoIP providers at a disadvantage over
traditional phone line services.

As well, a large number of VoIP providers are catering to wireless and satellite based Internet
Service Providers (ISP). The vast majority of these networks have problems with high latency
and jitter due to the distance being travelled by the wireless signal. As the fax standards
developed for fax machines do not provide any tolerance to the 200ms – 1000ms of latency
found on cellular and satellite networks, traditional FoIP products have a even lower success
rate (typically 50% or less) than found on cable or DSL internet connections.

Previous Methods for Faxing over IP

Method 1: Faxing using audio streams

As VoIP providers were not initially provided any specialized protocols for handling FoIP
communications, VoIP gateways used the G.711 muLaw or aLaw uncompressed voice codec to
transmit faxes over an IP network. Unfortunately, simply passing an analog fax signal through
a codec designed for voice communication produces an unpredictable result, resulting in a
large number of failures. As well, the high bandwidth requirements of G.711 are troublesome
in satellite Internet deployments where available bandwidth is kept to a minimum due to the

Most other audio codecs are unsuitable for fax transmission due to the nature of how the
compression is performed. The compression algorithms utilized in G.723, G.729, GSM, and
several other high compression algorithms are lossy compression techniques that degrade the
modem signaling to the point where faxing is nearly impossible. The G.726 is more suited to
handling fax signals as the 40 kbit/s audio stream can carry 12000 bit/s and slower modem
signals. However, as the fax process relies on tight timing tolerances, the latency and jitter
found in most Internet and wide area network (WAN) connections poses a challenge for
sending and receiving faxes using either G711 or G726.

As a result, the VoIP industry determined the only way using audio streams for faxing would
work with reasonable reliably is in local area network (LAN) deployments or in WAN
deployments employing fiber optic connections. As the vast majority of VoIP deployments do
not have this luxury, engineers looked to develop another method for sending faxes over IP.

Method 2: Faxing using T.37 Fax to Email Services

The T.37 fax protocol was developed as an ITU standard to provide an alternative method to
send faxes over IP that wasn’t subject to the issues created by latency and jitter on the IP
network. Service providers who offer this service commonly refer to the standard as "iFax",
"Internet Fax", or "Store-forward-fax".

A fax machine supporting T.37 will send a fax to an email address by converting the document
to a TIFF-F image, attaching it to an email (using the MIME format), and sending the
document using SMTP. The destination fax receives the email and prints the attached
document. Typically, the interface to the fax machine is done either through a RJ-11
connection to a standard fax machine or is built into the fax machine software itself.

While the fax service proved to be easy to use, there were a number of issues that kept it
from wide spread adoption:

       Email is a relatively insecure mechanism for sending and receiving faxes. As most
        email services did not (and still do not in most cases) employ either SSL or other
        encryption measures, there was no guarantee the fax would not be intercepted in
       There were no standard directory mechanisms to translate between phone number
        and email address. A standard is in development which allows a fax machine to use a
        destination fax number to look up an alternative email address. However, to this date,
        the standard has still not been ratified.
       Support for the T.37 standard in VoIP gateways were limited to expensive hardware
        devices and were not found in commodity hardware. Cisco was one of the biggest
        supporters of the protocol and continues to list the protocol as being supported in their
        IOS software.

Method 3: Faxing using the T.38 Fax Relay Protocol
The T.38 fax relay standard was devised in 1998 as a way to permit faxes to be transported
across IP networks between existing Group 3 (G3) fax terminals. The T.38 fax protocol
describes the process for sending and receiving faxes in real-time over a packet network. T.38
is designed to preserve the traditional fax experience and to allow faxes to be successfully
sent and received by making adjustments for jitter, latency and packet loss, which are
inherent in all IP networks.

T.38 Fax relay is where a T.30 fax device sends a fax over PSTN to a T.38 Fax gateway which
converts or encapsulates the T.30 protocol into T.38 data stream. This is then sent either to a
T.38 enabled end point such as fax machine or fax server or another T.38 Gateway that
converts it back to PSTN PCM or analog signal and terminates the fax on a T.30 device.

The T.38 standard is deployed in a large number of VoIP deployments throughout the world.
However, a number of issues have prevented wide spread adoption of the protocol:

       While T.38 is an ITU standard, this standard does not provide specifics on how it
        should be implemented. As a result, there have been a large number of compatibility
        issues with various fax machines. Some fax modems in PCs have been unable to
        recognize the fax tones on an incoming fax call from a device supporting T.38.
       Field testing has shown that T.38 fax relay using commodity hardware over Cable and
        DSL has a peak reliability rating of 70%. Over satellite internet connections, the same
        testing has shown the reliability drops as low as a 10% success rate.
      T.38 does account for packet loss through redundant packets and latency to a certain
       extent. However, it does not provide enough compensation for additional delay
       caused by high latency environments such as cellular or satellite data connections or
       network saturation/congestion in Cable/DSL environments. As fax devices are very
       sensitive to timing, faxing over connections with average latency times of 500
       milliseconds or more prove to be nearly impossible (as shown in field testing over
      If the remote unit running T.38 is unable to get an Internet connection, the remote fax
       user will be unable to send the fax to the remote. As T.38 is a real time faxing
       mechanism, there is no ability to store the fax in a “queue” and have it wait for the
       remote T.38 gateway to come back online before they can send their fax.

Method 4: Using a PC/Scanner combination

With the large number of problems found with FoIP solutions, some companies gave up on the
traditional fax machine and switched to sending scanned images to a fax server or over email.
With the prices of scanners being much lower than they were in the past, this method could be
setup with a small expense. However, this method had several major limitations:

      The process to get a multi-page image to the remote party takes a longer time to
       setup and send than it does through a fax machine. As a large number of scanners
       provided to users are single page scanners, each page has to be put on the glass
       individually. Even with multi-page document feeders, the scanned images often have
       to be reviewed and accepted before they are saved as image files and ready to be sent
       as an email or processed by a fax server.
      Because most installed email systems and fax servers are not interconnected,
       separate sets of software need to be setup and maintained on the user’s desktop to
       handle those functions. This creates a larger support demand for company IT
       departments due to confusion between the two systems and the extra labor required
       to maintain both systems.
      In a number of jurisdictions, a scanned image is not treated as a legally binding
       document while a faxed document is considered legally binding. In certain
       applications where contracts and/or legal documents are sent, emailing the image to
       the remote party is not an option.
                   Fax over IP Method Cost / Benefits comparison

Protocol                                      T.38 Fax                   Scanning                  SatFax
Reliability Rating Cable/DSL                     70%                       100%                     100%
Reliability Rating Cellular                      50%                       100%                     100%
Reliability Rating Satellite                     10%                       100%                     100%
Network Compatibility                          Limited                    Limited                   100%
Guarantees                                       None                       Yes                       Yes
Residential                                       Yes                       Yes                       Yes
Commercial                                      Limited                     Yes                       Yes
Bandwidth Minimum                              60 Kbps                    56Kbps                  2400 Baud
Legal Issues                                  Compliant                Non-compliant              Compliant
Time to send                                 10 seconds                  5 minutes                10 seconds
Provider Up Front cost                       $50,000.00                  Very high                    Call
Provider Recurring cost                      $50.00 mo                  IT Support                    Call
Support Costs                                    High                       High                     None
Loss of Business due to -                    Lost Faxes                 Office time                  None
Increased Revenues                               none                      none                      High
Convenience Factor                                low                       low                      High
Recommendations                                  None                       Few                      Many
      Note: Fax over audio stream was omitted from this comparison as it has been superseded by T.38 Fax
      Relay in most deployments and only has reasonable reliability in controlled network environments.

      The Solution - SatFax SF7000 Series Fax Terminal Adapters (FTA)

      The SF7000 series FTA provides a faxing solution that is simple and 100% reliable. The
      SF7000 adapters are small, compact units that provide your customer with standard telephone
      jacks that they plug their existing fax machine into. The SF7000 FTA utilizes the customers’
      internet connection to transport the images to and from the fax machine. For the customer,
      they send and receive faxes just like they always have (no technical expertise required).

      The SF7000 FTA provides a number of standard features expected from a VoIP adapter:

             True fax to fax functionality; simply drop in your fax, dial the number and press send.
              NO PC required! No scanning or attempts to attach & email the fax.
             Available in 1, 2, 4 or 8 ports
             Capable of providing both standard voice lines using SIP or fax lines using the SatFax
             Uses standard Ethernet cabling for network connectivity
             Automatically grabs line settings, software upgrades and provisioning from Virtutone
             A centralized web management system to control units, get call detail records (CDRs)
              and see if the unit is online and communicating
In addition to the standard features, the SF7000 series provides a number of features not
found in traditional environments:

          Able to utilize all types of internet connections including satellite and cellular data
          Able to fax from SatFax unit to SatFax unit without long distance charges
          All fax transmissions are 100% encrypted between the remote and the SatFax
           central network operations, ensuring your fax data is safe.
          Get a local fax numbers in one of 50 locations in Canada or one of over 1200
           locations in the United States without being physically located in that location
          Review fax transmission records real time (no waiting for the phone bill).
          Get “successful transmission” confirmations sent to you by fax or email confirming
           the remote fax was received by the other end.
          Send a copy of all incoming faxes to an email address and the fax adapter,
           allowing faxes to be received both electronically and on paper at the same time.
          Receive a backup copy of all your fax images for compliance purposes every
           month by using our Fax Backup service.

The benefits to the VoIP provider:
          Get 100% reliable fax service for your customer.
          Free your customer from his last Telco connection and complete your VoIP
          Remove customer apprehension about making the move to a VolP solution
          Drastically reduce the calls to your support group for fax related support issues.
          Increase revenues from your existing client base
Current SF7000 Series Models


The SF7100 is a one port unit that can handle one (1) voice OR fax line. It is important to
note that this unit will only handle voice or fax, but not both.

SF7100 Specifications
CPU: 400MHz Blackfin 532 Chip running uClinux
One analog (FXO/FXS) module interfaces to standard RJ11 port.
RS232 Connection for specialized applications
10/100 Ethernet port
NAND flash 256 M
12 V DC Power Supply


The SF7200 is a two port unit that can handle up to two (2) voice OR fax lines. As with
the SF7100, each port can be used for fax OR voice but not both. The unit also has a
second Ethernet port that allows another device to share the same Internet connection
without the need for a separate switch or router.

SF 7200 Specifications
CPU: 400MHz Blackfin 532 Chip running uClinux
Two analog (FXO/FXS) module interfaces to standard RJ11 ports.
Two 10/100 Ethernet ports (one WAN, one LAN)
NAND flash 256 M
12 V DC Power Supply


The SF7400 is a four port unit that can handle up to four (4) voice OR fax lines. This unit
is more versatile as each port can be configured independently. As with the SF7100 and
SF7200, each port can be used for fax OR voice but not both.

SF 7400 Specifications
CPU: 400MHz Blackfin 532 Chip running uClinux
One analog (FXO/FXS) module interfaces to standard RJ11 port.
RS232 Connection for specialized applications
10/100 Ethernet port
NAND flash 256 M
12 V DC Power Supply
How it Works

The SatFax FTA provides a store and forward fax service that captures the fax image at the
remote or at the central office before it is sent over IP. When the remote unit is transmitting
a fax, it emulates the dial tone of the land line and communicates with the local fax machine
using standard T.30 fax communication protocols. As the communication is all done at the
remote unit, the latency and jitter associated with the Internet connection are no longer a
factor, ensuring the communication to the attached fax machine is successful every time.

Once the fax is received, the remote converts the fax into a data file and sends it using a
encrypted file transfer across the IP connection to the SatFax Gateway. The SatFax Gateway
determines where the fax is to be routed and transmits the fax either over the SatFax network
or the Public Switched Telephone Network (PSTN) depending on whether the destination is
internal or external to the network. Once transmitted, the fax is stored in archives if the
remote user subscribes to our Fax Backup service or is purged if they do not. The system will
also send the remote unit a confirmation page to the remote fax machine if the user has
requested a comfirmation page be sent for each transmitted fax.

If the transmission is not successful to a PSTN destination, the SatFax Gateway will retry the
transmission to the PSTN fax machine over a 20-30 minute period. If the fax is unable to be
received at that time, the remote fax will be sent a “transmission unsuccessful” confirmation
page if the user has requested a confirmation page to be sent for each transmitted fax. If the
fax is destined for another SatFax unit, the fax will be held in queue for the remote unit to
grab on its next communication to the server.

On incoming faxes, the SatFax Gateway handles the receiving of the fax from the PSTN or the
remote SatFax device. Once the fax is received, the SatFax Gateway queues the fax image for
the remote to grab on its next transmission. The remote unit polls the SatFax Gateway every
5 minutes to see if there are faxes in the queue waiting for the remote. If a fax is waiting in
queue, the remote will grab the image file, ring the phone line on the port attached to the fax
machine and transmit the fax to the fax machine attached to the remote unit using standard
T.30 fax communication protocols. The SatFax gateway will send the confirmation page to the
PSTN or the remote SatFax unit that sent the fax if the user has requested that confirmation
pages be sent on incoming faxes. If the port attached to the fax machine is busy, the remote
will retry the fax over a 20-30 minute period. If the fax is not able to be sent to the remote
fax machine, the PSTN or remote SatFax user will be sent a “transmission unsuccessful”
confirmation page if the user has requested

As this is a store and forward faxing solution, there is a delay between the sending of the fax
from the remote and the reception of the fax at the destination. Typically, this delay is less
than 5 minutes from the time the image is received at the remote or received at the SatFax
Gateway. However, Internet connection conditions as well as network congestion may cause
the delay to be longer than 5 minutes in rare circumstances. All SatFax FTA units are
optimized for 14,400 baud communication with Error Correction enabled. If the fax machine is
only capable of a lower baud rate, the adapter will automatically adapt to accommodate the
speed of the remote fax machine.

Note: Error Correction is mandatory for communication over 7200 baud.

Why the SatFax Solution Is Right for You

Ask yourself these questions about your customer interactions:

       Are you tired of trying to sell your customers on the benefits of moving away from
        using the fax machine and into using a scanner, with little success?
       Are they telling you that they or their employees can’t or don’t want to take the extra
        time to learn to scan and email documents?
       Are your customers still insistent that they cannot get rid of the fax machine because
        all the companies they do business with use the fax for orders and reporting?
       Are they upset with you because you have all the answers to their VoIP questions but
        you still can’t get their overpriced fax line to work over IP?
       Are your customers frustrated and tired of being taken advantage of by the Telco that
        seems not to care about them or their business?
       Are the IT managers you talk to frustrated with fighting to get rid of the office fax
        machines and that they can’t manage it on their Ethernet Network?

The SatFax SF7000 series FTA is the faxing solution you need for your VoIP deployment. The
SatFax system provides a number of features that make it the ideal solution for your next Fax
over IP deployment:

       SatFax is Easy to use. Just use the fax like you always do. Dial and push send!
       Use any fax machine, new or old. The SatFax FTA has been 100% tested for
        interoperability and will work with any model.
   SatFax units are usable over any speed of network in both standard and high latency

   SatFax adapters are available in 1, 2, 4, and 8 port configurations
   Reduce your customers’ Network administration costs by using the SatFax FTA and not
    dealing with Telco invoices, wait times or installers that are costly.
   VoIP providers can increase revenues from your existing client base by providing a
    fully featured VoIP solution including fax services

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