What are ADSL filters?
A filter (or ‘z’-blocker) is a small electronic component that fits between your phone line and a regular voice device, such as a phone, a fax, or any device with a regular modem such as a cable box, alarm system or digital TV. With the ADSL service, all devices on that telephone number, except the ADSL modem, must be filtered. The filter protects the phone devices from high frequency noise. The filter is also there to protect the ADSL signal from noise contamination by high frequency noise added by analog phone devices. Some modems may come with a jack that is pre-filtered.
