DSL Distance Limits

DSL                       Max Data Rate       Distance (Feet/KM)
ADSL                    8M/1M                   18,000/5.5
VDSL                    52M/13M               4,500/1.4
IDSL                     144k/144k              18,000/5.5
SDSL                    768k/768k              22,000/6.7
G.SHDSL             2.3M/2.3M             28,000/8.5

Factors that affect distance:
Signal Attenuation
Bridge Tap - an extra telephone wirte with an un-terminated cable end connected to the local loop, can cause noise, reflection, raqdiate power to reduce signals and therefore speed
Local Coils - Wrap of excess wire along the local loop
Wire Gauage - thickness of wire, high speeds use thick wire
Impodence Mismatch - noise/echo on the line
Crosstalk - interference
AM Radio interference
Fibre Optics - ADSL signals cannot pass thorugh the conversion from Analog to Digital to Analog that occurs if a portion of the telephone circuit traverses fibre.