If you use a digital subscriber line (DSL) to access the Internet, you need DSL filters installed in the wall jack to separate the phone from the DSL signal. The filters block noise and static generated by the DSL signal coming in on the house telephone wiring.
DSL works to provide you with high speed access because the copper phone wires can support broader bandwidth transmissions than the 3.4 kHz phone signal. Using discrete multitone modulation, the copper phone wires carry DSL transmissions at up to 30MHz, according to Princeton University.
Telephone calls are carried by analogue signals and your DSL data is transmitted using digital signals. If the DSL filter isn't working properly, echoes from the analogue signal can cause DSL connection problems and reduced performance.
Telephones and fax machines interact with the phone line-in; the communication is two-way with the analogue devices connected to the phone lines. According to Old Home Tech Solutions, that's where the problem lies. The DSL signal is present at every phone jack and the DSL filter blocks the digital signal from contact with the analogue device connected to the splitter.
Bad DSL filters can result in poor phone performance because the filter is not blocking echoes from the DSL signal away from the telephone. These echoes can cause a lot of noise and static when you are making a call.
A DSL filter is a low-pass filter that allows the 3.0 to 3.4 kHz analogue phone signal to go to the analogue phone or fax devices attached to the line. It blocks the high frequency data signal by reducing its amplitude.
No Dial Tone
Sometimes a bad DSL filter will prevent you from getting any signal to the telephone. If you experience a loss of dial tone, try using a different filter. If that does not work, test the line coming in by plugging the phone directly into the wall jack. If the filter is bad, connecting the phone straight into the wall jack will give you a dial tone.
Belkin recommends unplugging everything and then plugging one DSL filter into the master phone jack. Attach both the line to a telephone and the line to your DSL modem to the filter and test the phone. If you still don't have a dial tone, the filter may be bad.
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