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No. Protection for... Surge protective device Part No.
Combined arresters for information technology systems
at the boundaries from LPZ 0 A (0 B ) ¨ LPZ 1 or area 0/A (0/B) ¨ area 1
BXT ML2 BE S 24 (2 cores + earth drain wire) 920 224
Alarm line groups, external alarms BXT ML4 BE 24 (4 cores) 920 324
(24 V) (in this case max. 0.75 A) + BXT BAS 920 300
+ SAK BXT LR (for earth drain wire) 920 395
BXT ML2 BD 180 920 247
Exchange line U K0 of the fixed-line operator
+ BXT BAS 920 300
Surge arresters for power supply systems at the boundaries from LPZ 0 B ¨ LPZ 1 or area 0/B ¨ area 1
a.c.TN-S system DG M TN 275 952 200
a.c. TT system DG M TT 2P 275 952 110
Table 9.9.1 Combined arresters and surge arresters in Figures 9.9.1 to 9.9.3

measures provide comprehensive protection against damage allows to connect the earth drain wire by means of an EMC
resulting from lightning strikes and surges (Figures 9.9.1 to spring terminal. For cables with more than two wires, a four-
9.9.3). wire version of type BXT ML4 BE … is available. Surge protec-
tive devices are selected according to the voltage of the alarm
Monitoring principles lines, which is typically between 12 and 48 V (Table 9.9.1).
Different monitoring principles are used for emergency alarm The low internal resistance of BLITZDUCTOR arresters is also a
systems: clear advantage since the maximum resistances of the alarm
¨ Pulse polling technology lines must not be exceeded.
Information from the detector which has triggered the For the outputs of the alarm panels (acoustic and visual alarm)
alarm is digitally transmitted. This allows to identify the it must be ensured that the nominal current of the surge pro-
detector and its exact location (Figure 9.9.1). tective devices is not exceeded.
¨ Analogue ring A telephone dialler is typically used if the alarm panel is
The addressable detectors define each detector in a ring. connected to the exchange line of a fixed-line operator e.g.
Line interruptions or short-circuits do not compromise the Deutsche Telekom. BLITZDUCTOR XT of type BXT ML2 BD 180
function (Figure 9.9.2).
is ideally suited for this purpose. The power supply system can
¨ d.c. circuit technology be protected by means of DEHNguard modular surge protec-
According to the closed-circuit principle, every alarm line tive devices (Table 9.9.1).
is permanently monitored. If a detector in a line is trig- Emergency alarm systems, which must be approved by the
gered, the line is interrupted and an alarm is produced in German Insurance Association (VdS approval), must comply
the alarm panel. However, only the alarm line, but not the with VDS 2095 (fire alarm systems), VDS 2311 (burglar alarm
individual detector can be identified (Figure 9.9.3). systems) and VDS 2833 (surge protective devices for emer-
Irrespective of the monitoring principle used, all cables extend- gency alarm systems).
ing between the different areas of the emergency alarm sys-
tem must be integrated in the lightning and surge protection The Executive Board or Executive Director of a company is re-
concept of the overall system. sponsible for the health and safety of all employees. In the
legal sense, a system operator is an ordinary person who is not
Recommended protection able to assess whether risks may arise from a technical solu-
BLITZDUCTOR XT of type BXT ML2 BE … must be installed to tion. Therefore, electricians, who provide technical solutions,
protect two-wire alarm lines (approval from the manufacturer must make sure in every single case whether their solutions
required, please contact DEHN + SÖHNE GmbH + Co.KG.) and meet the actual requirements.

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