Information Technology Reference
In-Depth Information
connector which is used to connect the handset to the telephone) or the RJ-45 (larger connec-
tor which is typically used in networked applications to connect a network adapter to a net-
work hub).
The characteristic impedance of a cable and its connectors are important, as all parts of
the transmission system need to be matched to the same impedance. This impedance is nor-
mally classified as the characteristic impedance of the cable. Any differences in the matching
result in a reduction of signal power and produce signal reflections (or ghosting).
Cross-talk is important as it defines the amount of signal that crosses from one signal
path to another. This causes some of the transmitted signal to be received back where it was
transmitted. Capacitance (pF/100 m) defines the amount of distortion in the signal caused by
each signal pair. The lower the capacitance value, the lower the distortion.
Table 2.2
Attenuation rates as a ratio
dB
Ratio
dB
Ratio
dB
Ratio
0
1.000
10
0.316
60
0.001
1
0.891
15
0.178
65
0.000 6
2
0.794
20
0.100
70
0.000 3
3
0.708
25
0.056
75
0.000 2
4
0.631
30
0.032
80
0.000 1
5
0.562
35
0.018
85
0.000 06
6
0.501
40
0.010
90
0.000 03
7
0.447
45
0.005 6
95
0.000 02
8
0.398
50
0.003 2
100
0.000 01
9
0.355
55
0.001 8
Attenuation (dB)
1
0.1
0.01
0.001
0.0001
Figure 2.6
Signal ratio related to attenuation
