The ADSL service is carried as a high-frequency signal on your ordinary phone line. This high-frequency signal is incompatible with your ordinary telephone and so a filter is required to keep the phone and ADSL signal apart. It is possible to fit just one filter at the point where the phone line comes into your building, to do this you will need to wire in the Face Plate Splitter. This may not be the best option for you if your computer is not near to the main phone point as all of your extensions will be filtered. An alternative strategy is to use a filter at each point where a phone is connected. If you plan to use this method the all-in-one splitter from Solwise is more elegant than the cumbersome dangly-wires products available elsewhere, though these types will work just as well. Note that you don't need a splitter at the point where your modem is connected. The modem can live quite happily with the low-frequency telephone signal. In fact the wires in the splitters American Style ADSL connection are just connected directly to the BT plug that goes into the wall. This means that if you don't have a phone plugged into the same point as your modem, you could save some money and just use a lead with a BT plug on the end to connect your modem. If this is not all clear, please feel free to email or call with your questions.