DSL filters block the DSL signal from reaching your phone, fax, and other devices. EXCEPT for your DSL modem, every device sharing the phone number that has DSL needs a filter. Unused jacks do not need a filter.
If you skip this step, you could experience noise and reduced phone service quality.
Some common devices that need DSL filters:
Regular phones
Cordless phones
Caller ID units
Answering machines
Fax machines
Dial-up modems
Satellite TV dialers
Meter readers
Monitored security systems that use the DSL phone line (check with your security company to determine if this is necessary)
