Use Fax over VoIP networks
VoIP technology converts the analog phone signal into digital bits. These are then assembled into
packets which travel on the Internet. The packets are converted and transmitted back to analog signals
at or near the destination.
Transmission of information on the Internet is digital instead of analog. Therefore, there are different
constraints on the fax transmission that might require different fax settings than the analog Public
Switched Telephone Network (PSTN). Fax is very dependent upon timing and signal quality, so a fax
transmission is more sensitive to a VoIP environment.
The following are suggested changes in settings for the HP LaserJet Analog Fax Accessory
500 when it is connected to a VoIP service:
Begin with the fax speed set in Fast (V.34) mode and with Error Correction Mode (ECM) turned
on. The V.34 protocol handles any changes in transmission speed needed to accommodate VoIP
If numerous errors or retries occur with the fax speed set to Fast, set it to Medium (V.17).
If errors and retries persist, set the fax speed to Slow (V.29) because some VoIP systems cannot
handle the higher signal rates associated with fax.
In rare cases, if errors persist, turn off ECM on the product. The image quality might decrease.
Ensure that the image quality is acceptable with ECM off before using this setting.
If the preceding setting changes have not improved the VoIP fax reliability, contact your VoIP
provider for help.
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