I am looking at making the change from dial-up to BB but not sure how many microfilters I need. I presntly have an extension telephone socket running to my pc which I have wired in to the back of the main telephone socket, this runs some 40 ft from the lounge to the dining room where my pc is. Running out of the front of the main socket I have a splitter, with one going to my telephone and one going to my Sky digibox. I am assuming that I only need one microfilter and that will be at the PC end of the hard wired telephone extension that I currently use for my internet connection. Sorry if this sounds daft!!