h. The attenuation of any pair depends on the parameters R, L, G, and C of the line and on the frequency.
Sometimes G or L, or both, are small enough to be negligible.
i. The loading of a transmission pair improves its response by increasing its series inductance. This may be
accomplished by use of loading coils (lumped loading), or by wrapping the conductors with a tape or wire of magnetic
material (continuous loading).
j. Cables and field wires are loaded by means of loading coils for military applications.
k. Interference in telephone circuits is of several kinds. Among natural causes may be listed lightning and other
natural atmospheric disturbances. Among other causes may be listed interference from adjacent telephone circuits,
possibly in the form of intelligible crosstalk or noise, and interference from nearby power or electric railway lines usually
in the form of noise.
l. Crosstalk and noise may be produced by magnetic, conductive, and capacitive coupling between adjacent
m. Interference may be minimized by careful installation of the line, by transpositions of the wires of the line, by
balancing the line capacitances, and by proper maintenance of equipment.