HP LaserJet Pro M521 Multifunction Printer series - Manual (Page 144)

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.
If faxing problems continue, contact the VoIP provider.
Fax memory contents are retained when there is a loss of power
The flash memory protects against data loss when a power failure occurs. Other fax devices store fax
pages in either normal RAM or short-term RAM. Normal RAM immediately loses data when power is
lost, while short-term RAM loses data about 60 minutes after a power failure occurs. Flash memory can
maintain its data for years without power applied.
130 Chapter 7 Fax ENWW