When you use the GE 26191 Wall Jack Adapter, it allows you to add an additional modular jack to an existing single-outlet modular jack. You can connect two modular phones by using the duplex adapter. A line for the Internet can be added on the same line with a phone when you use the duplex adapter. Having your phone and an accessory such as an answering machine, speaker phone or fax without installing a new jack is possible by using a wall jack adapter. The white adapter is a four-conductor unit. The simple plug-in design of the duplex adapter is easy to use. Regular phone cords plug into the GE 26191 Wall Jack Adapter to extend your line from single to double making it more efficient.