VARIOLITE Small Form Factor PC
User Guide - Precautions
Page 11
Electromagnetic Compatibility
This product meets the requirements of the European EMC Directive (89/336/EEC) and its amending
Directives, and the Low Voltage Directive 73/23/EEC. It is eligible to bear the CE mark. However,
because the unit can be installed in a wide variety of situations, certain conditions have to be applied to
ensure that the compatibility is maintained. Subject to those conditions, it meets the requirements for an
ITE Class A product.
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The VARIOLITE PC must be supplied with a clean AC supply, and the chassis should be connected
to a sound earth (ground). As a minimum the power cord must be connected to an earthed (grounded)
supply or outlet. Additionally, an earthing stud is provided on the chassis. It is good practice to
connect this independently to a suitable earth in fixed installations.
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When installing additional items, any recommendations made by the component
manufacturer/supplier must be complied with regarding earthing and the installation.
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The metal back plate of any expansion card must be securely screwed to the chassis of the computer
to ensure good metal-to-metal (i.e. earth) contact.
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All connector bodies must be securely connected to the enclosure.
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Most EMC problems are attributable to the external cabling. It is imperative that any external cabling
to the unit is totally screened, and that the screen of the cable connects to the metal end bracket of the
board or the enclosure and hence to earth. It is recommended that round, screened cables with a
braided wire screen be used in preference to those with a foil screen and drain wire. Use metal
connector shells that connect around the full circumference of the cable screen: they are far superior
to those that earth the screen by a simple “pig-tail” connection. This method attempts to extend the
enclosure around the connecting cables, thereby trying to surround the whole of the internal
equipment and external cabling.
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The keyboard and mouse will play an important part in the compatibility of the processor card since
they are ports into the board. Similarly, they will affect the compatibility of the complete system.
Fully compatible peripherals must be used otherwise the complete system could be degraded. They
may radiate or behave as if keys/buttons are pressed when subject to interference. Under these
circumstances it may be beneficial to add a ferrite clamp on the leads as close as possible to the
connector.
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USB cables must be high quality screened types suitable for USB 2.0, and peripherals must be
approved to equivalent EMC standards.
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Where possible ensure that the screens of any external cables are also bonded to a good RF earth at
the remote end of the cable.
Failure to observe these recommendations may invalidate the EMC compliance.