The listing, 2Wire DSL filter has ended.
An Internet service provider using 2Wire products may provide you with 2Wire DSL filters when you subscribe to its service. For example, AT&T, an ISP that offers DSL service through the 2Wire gateway, provides its customers with these filters. There are several single filters, and one dual filter. The dual filter allows you to plug the modem and another device into the same jack, and a single filter allows only one device to be plugged into the jack. You plug the dual filter into the telephone jack intended for the DSL modem. Plug the modem itself into the "DSL" port on the filter, and any other device you wish to share that jack into the "Phone" port on the filter. Connect all the single filters into other jacks using the same line as the modem, and then plug devices into those filters. Don't plug your 2Wire gateway itself into either the single filters or into the "Phone" side of the dual filter. Doing so erases the gateway's signal, meaning no Internet connection.