Quote Originally Posted by DocPC
You only need the filter on the phones, not the modem/computer........

The filter converts digital to analog. ALL your phone lines are digital if you have DSL.

Asymmetrical Digital Subscriber Line provides always on Internet access over your existing phone line. Using a special ADSL modem and line filters, the frequency bands that are available on the copper phone line are expanded to enable higher speeds. ADSL uses frequency bands between 0 and 4 Khz for your telephone service and 20 Khz to 2.2 Mhz for your ADSL service - this is how you are able to use both ADSL and your telephone at the same time. Filters are used on phones to filter frequencies higher than 4khz from being sent to the phone. ADSL is analog, so don't be misled by it's name. ISDN is digital. T1's and T3's are digital, but not ADSL.