If all the available Ethernet jacks in your DSL or digital cable modem are already being used (by a computer, for example), then you will need to use a Router (sold separately). A Router allows you to connect more than one device to your Internet service (for example, connecting both your computer and your CapTel 800i to the Internet at the same time). A Router plugs directly into the Internet service DSL or digital cable modem. Then you plug the CapTel 800i into the Router, along with any other devices that require Internet access.