Yes. DSL works by sending an "out-of-band" signal on your regular phone line. 56k Modems operate in the normal voice range of a standard phone line ( ~150 - ~3500hz). DSL adds a signal at much higher frequencies. (That's why not everyone can get DSL - if your phone line is long and has load coils, they attenuate any higher frequencies; lines served by digital carrier (SLC, DLC, etc.) also cannot
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