Sharing a DSL connection with analog telephones may cause interference. DSL Filters eliminate all interference between your DSL line and analog telephone lines. The result is clear, clean lines for your telephones, fax machines, answering machines, Caller ID, and analog modems. DSL Filters also ensure that telephones never cause the DSL modem to adjust to the changing conditions of your DSL connection, which could hinder your Internet access speeds. Wall-mount DSL Filter is used when connecting a wall-mount phone.