It depends. Assuming that everything was installed to specification,
the fourth load point would be at 21,000 feet from the telco. The
load points are where load coils are placed by the telco to suppress
exactly the signal that DSL modems need to transmit high speed data on
-- high frequency. The standard is for them to be placed every 6,000
feet, starting 3,000 feet from the central office. However, it
appears that they may not all be placed evenly, or correctly. The
following article details one engineers difficulties:
Outside Plant Magazine June 1999, Cleaning Up Old Analog Plant for
Digital Transport, by Don McCarty
DSLReports.com defines Load Coil and provides the specification for
Steve Elisberg (firstname.lastname@example.org) posts in comp.dcom.isdn that:
"The most common loading scheme used by the "Bell System", was H88.
That is, an 88 millihenry choke is placed at 6000' intervals. The
first is placed at 3000' from the central office. Thus, the "Load
Points" would be at 3kf, 9kf, 15kf,
21kf, 27kf and so on."
Don Kimberlin (email@example.com) posts a great history of load
coils in comp.dcom.telecom at this URL:
The IEC provides a nice overview of load coils with graphics to help
illustrate their use at:
I hope this answers your question; if you need further information,
please ask for clarification before rating this answer.
pots distance load point @ Google Groups:
and at Google Web:
"Load Point #4"