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IT cabling 100 Ω (Cat. 3, 5, 6, ...)
Horizontal cabling
– Connecting cable between FD and TO
– Transmission performance up to
250 MHz (Category 6)
TO Telecommunication outlet
FD Floor distributor TO TO
BD Building distributor TO FD
Building backbone cabling
– Connecting cable between BD and FD external
lightning
protection
FD system

FD FD

FD BD CD

optical fibre cabling (data)

copper cabling (telephone)
Figure 8.2.3.2 Lightning interference on the IT cabling

Optical fibre cables are typically used as data connection be- The protective devices required for this purpose must be se-
tween the campus and building distributor. This means that no lected according to the network application. Common network
surge arresters (SPDs) are required for the field side. If, how- applications are:
ever, the optical fibre cables have a metal rodent protection, it ¨ Token ring
must be integrated in the lightning protection system. The ac-
tive optical fibre components for distributing the optical fibre ¨ Ethernet 10 Base-T
cables, however, are supplied with 230 V on the power side. In ¨ Fast Ethernet 100 Base-TX
this case, SPDs for power supply systems can be used. ¨ Gigabit Ethernet 1000 Base-TX

Nowadays, the building backbone cabling (between the build-
ing distributor and the floor distributor) almost exclusively 8.2.4 Intrinsically safe measuring circuits
consists of optical fibre cables for the transmission of data.
However, balanced copper cables (also referred to as master Special explosion protection measures must be taken in all in-
cables) are still used for voice transmission (telephone). dustrial sectors where gas, vapour, mist or dust form a hazard-
With a few exceptions, balanced copper cables are nowadays ous explosive atmosphere with air during the processing or
used for the horizontal cabling (floor distributor and terminal transport of flammable substances.
equipment).
Depending on the probability and duration of the presence of
For cable lengths of about 500 m (building backbone cables) an explosive atmosphere, the areas of an Ex system are divided
or about 100 m (horizontal cables), direct lightning strikes to into zones – also referred to as Ex zones.
the building (Figure 8.2.3.2) can induce high common-mode
interference which would overload the insulation strength of a Ex zones
router and / or an ISDN card in the PC. In this case, protection Ex zones with areas where hazardous explosive atmospheres
measures must be taken both for the building / floor distributor arise due to e.g. gases, vapours and mists are divided into
(hub, switch, router) and the terminal equipment. Ex zones 0 to 2 and those in which hazardous explosive at-

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