I have a hard wired wall mounted telephone (not modular). I need to insert a DSL modular filter into the circuit. What do I need to do convert the hard line to a modular line so I can insert the DSL filter?

follow these steps : 1. Power off your computer. Connect the modem to the signal source. If the source is a cable signal, connect the modem with a cable wire. If it's a DSL signal, connect it with a telephone wire.
2. Connect the proper ends of the USB wire to the USB ports on the modem and the computer.
3. Connect the ethernet cable to the modem and the computer.
4. Insert the power source into the modem and then plug it into the wall socket or the series circuit.
5. Wait until all the lights on the modem are lit and then turn on the computer. When the Hardware Wizard detects the new device, you may have to insert the disk that came with it to install the software for the device. This will complete the connection of the modem to the computer.

Telephone your Internet Service Provider, and have them check that you've paid your monthly fees, and that the DSL-modem at "their" end of your telephone-circuit has not failed.

Try a different DSL-modem, to see if your particular modem has "died".

Check the 2-strand or 4-strand wire from the DSL-modem to the wall-outlet, to make sure that it is properly connected.

Try a different 4-strand wire.

Hi
This is Neo . Check the Filters in the phone line if you have installed the filter . if there is no filters before the telephone , install a filter . Whether the phone line are connected properly and check the wall point where the connection from the DSL and telephones . Check the cords and try changing the RJ11 cords . RJ cors the phone thin cords .
NOTE : FILTERS SHOULD BE INSTALLED FOR TELEPHONES BUT NOT FOR 2 WIRE .

1. Ensure that your AT&T DSL self-installation kit is complete. At minimum, it should contain a DSL modem, an AC adapter, an Ethernet cable, a telephone cable, several telephone filters and an installation CD.
   
2. Install the telephone filters on each telephone jack that you have a phone plugged into. Install a dual phone adapter on the jack closest to your computer if you have an answering or fax machine, telephone or analog modem in the same room. Then plug your telephone equipment into the filters. Connect the telephone cable that was provided with your installation kit into an unfiltered telephone jack.
   
3. Insert the installation CD into your CD-ROM drive. If the installation program does not start automatically, click Start > Run > and browse to the CD-ROM drive directory to find the installation file.
   
4. Connect the telephone cable that is attached to the unfiltered wall jack to the back of the DSL modem. Connect the Ethernet cable to the back of the modem and to the Ethernet network interface card port on the back of your computer. Connect the AC adapter to the back of the modem and plug it into an electrical outlet. Power the modem on.
   
5. Check the modem lights. There should be at least two lights lit. These will have labels such as "Power" and "Ethernet." However, these labels may differ depending on the model of modem you received in your installation kit.
   
6. Complete the software installation. Enter your chosen username and password when prompted. Check your modem to see if the light labeled "DSL" or "Internet" is lit. Open a web browser window to see if your DSL service has been successfully installed.
   

Install a DSL-filter between the telephone wall-jack and the telephone-port on the printer.

There is not enough information in your question to diagnose properly the source of interferences. I will however venture an educated guess. If your broadband internet connection is some form of DSL you must put filter on all the telephone sets. In other words, the telephone line going from the wall to a telephone set must pass through a DSL filter.
If I made a wrong guess, do not impale the answer; post a comment instead.

That would be a DSL phone filter. It is needed to eliminate modem noises from telephone. The filter plugs into the wall socket and your telephone plugs into the filter. Most electronics stores sell them.
http://en.wikipedia.org/wiki/DSL_filter

Sounds like some bad copper wire somewhere:

Try replacing the telephone wire between the fax machine and the wall.
If you have dsl, make sure the fax phone wire is plugged into a filter.
Try setting the fax machine to transmitreceive at a slower speed.
This could indicate a problem with your phone wires. Is there static on your phone line?
Maybe give your telephone company a call and have them check the line(s).

Hope this helps!

Yes - you need the DSL filter in jack you plan to use (you need them in any jack with a phone/fax connection. It matters not that the handset is cordless - the connection to the wall needs the filter or your DSL will a) not work or b) work poorly

To test your fax setup
1 Press Setup.
2 Press 6, and then press 5.
This displays the Tools menu and then selects Run Fax Test.
The HP all-in-one displays the status of the test on the color graphics display and prints a report.

3 Review the report.
– If the test passes and you are still having problems faxing, check the fax
settings listed in the report to verify the settings are correct. A blank or
incorrect fax setting can cause faxing problems.
– If the test fails, review the report for information on how to fix any problems
found. For more information, you can also see the next section, The fax test
failed.
4 Press OK to return to the Setup Menu.

Make sure you used the phone cord supplied in the box with your HP all-in-one
to connect to the telephone wall jack. One end of this special 2-wire phone
cord should be connected to the port labeled "1-LINE" on the back of your
HP all-in-one and the other end to your telephone wall jack

This special 2-wire cord is different from the more common 4-wire phone cords
you might already have in your home or office. Check the end of the cord and
compare it to the two types of cords shown below.

If you used the 4-wire phone cord, disconnect it, find the supplied 2-wire cord,
and then connect the 2-wire cord to the port labeled "1-LINE" on the back of
your HP all-in-one. For more information on connecting this phone cord and
setting up your HP all-in-one for faxing, see Fax setup.
If the supplied phone cord is not long enough, you can extend it. For
information see The phone cord that came with my HP all-in-one is not long
enough.
● Try connecting a working phone and phone cord to the telephone wall jack
that you are using for the HP all-in-one and check for a dial tone. If you do not
hear a dial tone, contact your telephone company and have them check the
line.
● Other equipment, which uses the same phone line as the HP all-in-one, might
be in use. For example, you cannot use your HP all-in-one for faxing if an
extension phone is off hook, or if you are using your PC modem to send an email
or access the Internet.
● The phone line connection might be noisy. Phone lines with poor sound quality
(noise) can cause faxing problems. Check the sound quality of the phone line
by plugging a phone into the telephone wall jack and listening for static or
other noise. If you hear noise, turn Error Correction Mode (ECM) off and try
faxing again. For information, see Use error correction mode. If the problem
persists, contact your telephone company.
● If you are using a digital subscriber line (DSL) service, make sure that you
have a DSL filter connected or you will not be able to fax successfully. The
DSL filter removes the digital signal and allows your HP all-in-one to
communicate properly with the phone line. Obtain a DSL filter from your DSL
provider. If you already have a DSL filter, make sure it is connected correctly.
Make sure your HP all-in-one is not connected to a telephone wall jack that is
set up for digital phones. To check if your phone line is digital, connect a
regular analog phone to the line and listen for a dial tone. If you do not hear a
normal sounding dial tone, it might be a phone line set up for digital phones.
● If you are using either a private branch exchange (PBX) or an integrated
services digital network (ISDN) converter/terminal adapter, make sure the
HP all-in-one is connected to the port that is designated for fax and phone
use. Also, make sure that the terminal adapter is set to the correct switch type
for your country/region, if possible.
Note that some ISDN systems allow you to configure the ports for specific
phone equipment. For example, you might have assigned one port for
telephone and Group 3 fax and another port for multiple purposes. If you
continue to have problems when connected to the fax/phone port, try using the
port designated for multiple purposes; it might be labeled "multi-combi" or
something similar. For information on setting up your HP all-in-one with a PBX
phone system or ISDN line

you may also refer to the manual for this unit here
if you go there please refer to page 82 of the manual or chapter 10