Identify devices that require a filter Filters block the DSL signal from reaching your telephone, fax, or answering machine. Except for your DSL modem or wireless router, every telephone machine sharing the phone line that has Verizon High Speed Internet requires a filter. If filters are missing, you may experience reduced speeds as well as static or hissing on the telephone line.
Note: Using more than five filters can reduce the quality of your Verizon High Speed Internet service.
Where do I install filters?
Other common devices that need filters:
If you need additional filters: