ADSL line filter is a minimum requirement for a reliable ADSL based Internet connection. It also removes annoying interference caused by a DSL connection. It is usually required for telephones, fax machines and other equipment that share the same phone number as the DSL connection. Simply connect the filter in between the phone line's wall socket and your phone/fax or other equipment which use RJ-12 connectors. You may need a filter on each phone outlet. A-Tick approved and complies to the latest amended standard (AS/ACIF S002:2001 Amended). Full instructions provided.