Are you using a surge-protection device?
This is a device that is used between the jack in the wall and the device to protect the
device against electrical power that passes through the telephone lines. These can cause
some fax communication problems by degrading the quality of the telephone signal. If you
are having problems sending or receiving faxes and are using one of these devices,
connect the device directly to the telephone jack to determine if the problem is with the
surge-protection device.