990DSL
Users Guide
4-42
Power Harmonics Test
The Power Harmonics test is available as a softkey test option on the VF Noise
test result screen. The test shows values of both odd and even power frequency
harmonics in the voice frequency band.
After running the VF Noise test, press C(
Power Harmonics) to obtain a
snapshot graph of all power frequency harmonics on the line. The test is made
from Tip and Ring to Ground, with optional C-Message filter and units of
measure selected in VF Noise Setups. The fundamental frequency (50 / 60 Hz)
is automatically derived from the selected Language / Country in
USER
OPTIONS.
Figure 4-25 illustrates a typical set of Power Harmonics on a working POTS
pair with a normal degree of harmonics, due to inductive power line coupling.
acy99s.eps
Figure 4-25. Power Harmonics Test Results
Note that the fundamental coupling frequency (60 Hz) is the largest signal
present, as is normally the case when electromagnetic fields around power
lines couple inductively into the telephone cable. With normal inductive
coupling, the odd harmonics (3
rd
, 5
th
, 7
th
, etc.) are predominant, and have
exponentially decreasing levels as shown in Figure 4-25.
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