Figure C-3: Example of Grounding Shielded Cable at Only One End
Grounding and Connectors CK721-A Installation and Operation
C-4 24-10349-8 Rev. B
This document contains confidential and proprietary information of Johnson Controls, Inc.
© 2012 Johnson Controls, Inc.
Installations in Europe
All Cardkey equipment panels must be connected to a proven building electrical
system ground (earth).
Connect the shield of low voltage and data sy
stem cabling to ground at only one end
(see Figure C-3). This is generally at the higher end of the system hierarchy.
Cables to user peripherals (printers, VDTs, etc.)
should have shields connected at
both ends.
Separated wires of
cable are not shielded
The screen-type shield is
inside the enclosure, no
more than 2" (5cm)
Short wire is
connected
from shield to
enclosure of
unit 1
No connection of
shielded cable
UNIT2
UNIT1
PCBA
CARD READER UNIT GROUNDING
If the card reader unit ground is not mounted on a metal surface, connect a grounding wire to
the card reader unit housing. Run the wire to the associated unit, and as shown in Figure C-3,
connect the cable shield to the grounding bus. The scre
ws for the ground bus are bagged
separately for installation.
If the card reader unit is mo
unted on a metal surface which may contact ground, select either
one of two options:
 Insulate the card reader unit from the metal surface and connect the grounding wire
described above.
 Leave the card reader attached to the metal surface if insulating it is not practical,
and do not connect the grounding wire described above. This will prevent a possible
ground loop or other problems, since building framework or structural metal is often
subject to stray AC or DC voltages and transients.
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