How to Detect Missing DSL Filters

Don't place a filter on the DSL modem's phone cable.

DSL modems use the phone lines in your house to transmit and receive information from the Internet. Because they share phone lines, DSL and voice signals sometimes interfere with each other when they are used at the same time. DSL filters installed on your phones, fax machines and other devices prevent the signals from interfering with each other. Missing even a single DSL filter dongle can dramatically decrease your DSL modem's Internet connection quality. Fortunately, detecting missing DSL filters is simple.

Instructions

1. Open a web browser window and go to one of the speed test sites linked in the Resources section. Select a location near your address if given a choice and click "Start" or "Begin" to run the speed test. Note your Internet connection's speed rating.

2. Make a phone call using one of your home phones to your cell phone or a friend who won't mind having his phone line tied up for a few minutes.

3. Run the speed test again while still on the phone. If your performance is noticeably slower, that phone is probably missing a DSL filter.

4. Go to the phone you were using and follow its telephone cable to the outlet into which it is plugged.

5. Look for a DSL filter dongle connected to the phone outlet. Most DSL filters are small boxes with a telephone cable coming out of one side and a phone jack in the other. If the phone is plugged directly into the wall outlet, you're missing a DSL filter.

6. Repeat this process with every phone, fax machine, answering machine or other device connected to the phone outlets in your house. Your DSL modem should not have a DSL filter on its phone outlet.

Tips & Warnings

• If your phone outlets are visible and easy to access, you can skip the speed testing steps and just examine the outlets.

References

• Home Phone Wiring: DSL