OK, so exactly what is a DSL Filter and why is it needed and how do they work?
Riss Centaur’s 50-cent DSL Filter Primer: Way back in the dim reaches of time, the good old Bell System (Alexander Graham Bell, The Telephone Company, Ma Bell, Western Electric, Before Divestiture, the Big Breakup, whatever….) came up with the standard for the VOICE BAND or POTS (Plain Old Telephone Service) that all telephones should handle throughout the system. It was decided that telephones would need to carry signals from about 300Hz (cycles) through to about 3,300Hz. This is the range that is needed for intelligible speech. (In truth, the phone line band is 0 to 4,000Hz, just to be safe and carry touch tones.) This is also why music, with its higher frequencies (up to 20,000Hz) sounds lousy over a phone – because you lose the high frequencies. Ok, so voice is in the band of 300-3,300Hz. Where is DSL? ADSL uses the frequencies from about 26,000 (26K) to 1,100,000 (1,100K) Hz. These much higher frequencies are outside of human hearing, but when shoved down the phone wires can car
