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5
Installing the communication cables
Installing the communication cables
When using galvanic connection between protection terminal and communication
equipment or point to point galvanic connection between two protection terminals it is
essential that the cable installation is carefully done. This is true regardless of type of
module used, G.703, V.36, short range galvanic etc., only the possible length of the ca-
ble differs. The factors that must be taken into account is the susceptibility for noise dis-
turbance, due to that the levels of the communication signal are very low.
For best result a cable with twisted pairs and double screens should be used, one screen
for each twisted pair and one surrounding all pairs. Each signal shall utilizing its own
twisted pair as in figure 6. The screen for each separate pairs shall be connected to in-
ternal screen or ground connection of equipment, if available, or in other case connected
to earth close to the equipment at the sending end for the signal. At receiving end the
screen shall be left floating, that is, not connected to earth.
The outer screen surrounding all pairs shall be connected to a solid earth at each end
close to the equipment.
Lc
Rx
Tx
Sc
Cc
Communication cable
Lc
Line connector
Rx
Receive input
Sc
Screen (or earth/ground) connection
Tx
Transmit output
Figure 6: Communication cable installation
Cc
Chapter 5
Installing the terminal
Lc
Tx
Rx
Sc
en01000160.vsd
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