Hi Claudia, The phone filters are to prevent extraneous noise from penetrating into the telephone conversations.
If you don't place the filters on the line, when ever you use the telephone for anything, you may be subject to computer noises, or static on the line. While it does not happen in all instances, it does happen frequently. The ISP figures it's cheaper to just send out phone filters, instead of paying someone to answer customer support questions when they get this noise on the line. If you received the filter from your ISP, ask if they can provide extra ones for the other phones you have in the house, and if they can't, find out how much they'll charge you for them, as it may be cheaper going to them, and better quality of filter also. Mind you, this isn't always true, so be careful, and make sure to shop around. Victor Gouveia
