Use this RJ11 to BT RJ11 Adapter to split one RJ11 socket to a RJ11 socket and a BT socket. It allows one modem with a RJ11 plug and one telephone or modem with a UK plug to connect to a single RJ11 telephone socket. This RJ11 BT Adapter is very simple to use. You just plug the adaptor into the RJ11 phone socket, and plug your RJ11 cable or BT cable (not supplied) into the adapotor, and thats it your done! One end is 6P4C RJ11 plug and the other end is one 6P4C RJ11 socket and one 6P4C BT socket.