If you have a Cisco 827-4V router, you can connect analog telephones or fax machines to your router. Use the cables provided with these devices.
The gray PHONE 1, 2, 3, and 4 ports are RJ-11 connectors. If you are outside North America, you must buy and attach adapters that allow telephones or faxes to be connected to the RJ-11 connectors. In some countries, these adapters need additional electronics to convert the telephones or faxes to work properly with the router phone ports. For example, in the United Kingdom, you must buy an adapter that also provides a master socket, which causes incoming calls to ring the connected devices. For information on recommended master sockets, see the Cisco 827 and SOHO 77 Routers Hardware Installation Guide.