Back in the days before electronic amplification telephone systems were
peaked to work with less loss at around 1000 Hz. Made them tinny but
at least you could hear the other person. Before multi cable all was open
line
and the lines were also crossed. This made them balanced as well as
providing
less noise coupling and the proper impedance for the transmission
and less loss of the voice peaked at 1000 Hz. Before Digital switching
,,,trunk
circuits were still toned out at 1000Hz . That is still a standard today
but we no
longer use open wire. So the idea that power lines and telephone lines
are
transmission lines holds true just like the transmission line used for RF
.
Bob K3DJC
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