For example, with ADSL, data can be
downloaded faster than they can uploaded. The terms
(a)symmetrical and (a)synchronous are also used in
relation transmission systems such DSL.
In symmetrical data transmission, instead one data
cable, two data cables are used carry signal, for
example the case Twisted Pair cables. The two
wires are 180° out phase. this case the signal voltage
changes relation reference potential/earth. These
terms refer the symmetry synchronicity the
data rate. During downlink/download, the data rate
generally differs considerably from that during up-
link/upload.6 Symmetrical and asymmetrical data transfer
Asymmetrical interfaces consist data conductor
and earth wire. Supply lines such energy and data
cables often run through all the zones. fault coupled onto
a signal-carrying wire, will couple onto the second
wire well. In
SDSL the two data rates are the same.1.7 Device protection classes
Objects risk from lightning and surge voltage are
classified into lightning protection zones (LPZs).TBS
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Asymmetrical cable
Cable jacketing
Insulation wire A
Insulation wire B
Conductors wires A/B
Symmetrical cable
Energy cable
Data cable
Equipotential bonding system
Cables passing through all lightning protection zones
3. Due the phase difference, the interfer-
ence signal virtually cancelled out. The
aim these LPZs reduce the amplitude the
lightning current/surge voltage individual zones to
at least value the voltage resistance the devices
in that zone.
A suitable surge protection device must chosen for
each zone.
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233
Chapter The internal lightning protection system
.3.1. The protection class marked many
OBO surge protection devices.3.
3
