Load Coils are devices out on
telephone poles that filter out
line noise. Around here they are placed every 18,000
feet.
On the
PSTN voice communications occur in the
frequency range of 0-4
khz. What a load coil does is filter out anything that may
interfere with the voice transmissions. It is for this reason that around here the max range for
DSL is 18,000 feet. DSL operates at frequencies above the voice frequencies (1 - 25
mhz). If a DSL hit one of these load coils, it would be filtered out and your DSL would cease to function.