An ADSL filter is normally a small plastic box with a short lead that plugs into your phone socket and two outputs, one for your ADSL Modem. The operator install ADSL system to the central office, they install ADSL splitter filters on the central office end of the telephone wire. The filters at the central office have basically the same functional needs as the home units, they need to be able to keep different signals separate, and separate those two signals to different outputs.
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