21. Technical specifi cations
21.1. Key to symbols
Protection class II
Electrical devices in protection class II are devices that have dou-
ble and/or reinforced insulation throughout, and do not have the
option of connecting a protective earth. The housing of an electri-
cal device in protection class II, with surrounding insulating materi-
al, may either form all of the additional or reinforced insulation, or
part of it.
Indoor use
Devices with this symbol are intended solely for indoor use.
Polarity markings
Fig. A
In the case of devices with coaxial power connectors, these symbols
indicate the polarity of the connector. There are two types of polar-
Fig. B
ity: either positive inside and negative outside (Fig. A), or negative
inside and positive outside (Fig. B).
CE labelling
Products that feature this symbol meet the requirements of the EU
directives (see chapter entitled "Declaration of conformity").
Tested safety
Products that feature this symbol meet the requirements of the Ger-
man Product Safety Act.
Symbol for direct current
Symbol for AC current
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