HP LaserJet Pro 400 MFP M425 - Manual (Page 106)

Use fax on a DSL, PBX, or ISDN system
HP products are designed specifically for use with traditional analog phone services. They are not designed to
work on DSL, PBX, ISDN lines, or VoIP services, but they work with the proper setup and equipment.
NOTE: HP recommends discussing DSL, PBX, ISDN, and VoIP setup options with the service provider.
The HP LaserJet product is an analog device that is not compatible with all digital phone environments
(unless a digital-to-analog converter is used). HP does not guarantee that the product will be compatible
with digital environments or digital-to-analog converters.
DSL
A digital subscriber line (DSL) uses digital technology over standard copper telephone wires. This product is
not directly compatible with those digital signals. However, if the configuration is specified during DSL setup,
the signal can be separated so that some of the bandwidth is used to transmit an analog signal (for voice and
fax) while the remaining bandwidth is used to transmit digital data.
NOTE: Not all faxes are compatible with DSL services. HP does not guarantee that the product will be
compatible with all DSL service lines or providers.
A typical DSL modem employs a filter to separate the higher frequency DSL modem communication from
lower frequency analog phone and fax modem communication. It is often necessary to use a filter with
analog phones and analog fax products that are connected to a telephone line used by a DSL modem. The
DSL service provider usually provides this filter. Contact the DSL provider for more information or for
assistance.
PBX
The product is an analog device that is not compatible in all digital phone environments. Digital-to-analog
filters or converters may be needed for faxing functionality. If faxing issues occur in a PBX environment, it
might be necessary to contact the PBX provider for assistance. HP does not guarantee that the product will
be compatible with digital environments or digital-to-analog converters.
Contact the PBX provider for more information and for assistance.
ISDN
The product is an analog device that is not compatible in all digital phone environments. Digital-to-analog
filters or converters may be needed for faxing functionality. If faxing issues occur in an ISDN environment, it
might be necessary to contact the ISDN provider for assistance. HP does not guarantee that the product will
be compatible with ISDN digital environments or digital-to-analog converters.
Use fax on a VoIP service
Voice over internet protocol (VoIP) services are often not compatible with fax machines unless the provider
explicitly states that it supports fax over IP services.
If the product experiences problems getting a fax to work on a VoIP network, verify that all cables and
settings are correct. Decreasing the fax-speed setting might allow the product to send a fax over a VoIP
network.
If the VoIP provider offers a "Pass through" mode for the connection, that will offer better fax performance
on VoIP. Also if the provider has "comfort noise" added to the line, fax performance can be enhanced if this
feature is not enabled.
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