There are 2 ways you might have it.
Key.
Network Cable= RJ45 and is 10/100/1000mbs band width.
RJ11= old
1. BT give you a USB Modem, which one end has a USB cable which you then put into your pc, and the other end you have what seems to be a cable which used to be used for 56K modems. But now is used for conecting from the filter to the modem which BT Gave you.
2. You have got a ADSL Modem Router, which also has which seems to be a old cable which used to be used for 56K modem cards. But now is used for conecting from the filter to the ADSL Modem Router. Out of these ADSL router should be ports for connecting RJ45 Cables which are network cables basicly. These then connect into your pc via the LAN card or the onboard LAN on your motherboard.