services are often not compatible with fax machines. The VoIP provider must state that the service
supports fax over IP services.
Because the installation process varies, the VoIP service provider will have to assist in installing the
product fax component.
Although a fax might work on a VoIP network, it can fail when the following events occur:
●
Internet traffic becomes heavy and packets are lost.
●
Latency (the time it takes for a packet to travel from its point of origin to its point of destination)
becomes excessive.
If you experience problems using the fax feature on a VoIP network, ensure that all of the product
cables and settings are correct. Configuring the Fax Speed setting to Medium(V.17) or Slow(V.
29) can also improve your ability to send a fax over a VoIP network.
If you continue to have problems faxing, contact your VoIP provider.
The fax subsystem
The formatter, fax card, firmware, and software all contribute to the fax functionality. The designs of the
formatter and fax card, along with parameters in the firmware, determine the majority of the regulatory
requirements for telephony on the product.
The fax subsystem is designed to support V.34 fax transmission, low speeds (such as V.17 fax), and
older fax machines.
Fax card in the fax subsystem
Two versions of the fax card are used in the product. One is used in the North American, South
American, and Asian countries/regions. The other is used primarily in European countries/regions.
The fax card contains the modem chipset (DSP and CODEC) that controls the basic fax functions of tone
generation and detection, along with channel control for fax transmissions. The CODEC and its
associated circuitry act as the third-generation silicon data access arrangement (DAA) to comply with
worldwide regulatory requirements.
The only difference between the two versions is that each version is compliant with the 2/4-wire phone
jack system from the respective country/region.
Safety isolation
The most important function of the fax card is the safety isolation between the high-voltage, transient-
prone environment of the telephone network (TNV [telephone network voltage]) and the low-voltage
analog and digital circuitry of the formatter (SELV [secondary extra-low voltage]). This safety isolation
provides both customer safety and product reliability in the telecom environment.
Any signals that cross the isolation barrier do so magnetically. The breakdown voltage rating of barrier-
critical components is greater than 5 kV.
24 Chapter 1 Theory of operation ENWW
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