GarrettCom MAGNUM 6KQE - Manual (Page 49)

Magnum 6KQE Managed Edge Switch Installation and User Guide 02/09
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C3.0 DUAL-SOURCE OPTION, THEORY OF OPERATION
The Dual-Source DC power option is designed using diodes inside of the
chassis on each DC power input line. A diode is placed in each of the four input lines
(behind the four external power
connection terminals) so that
power from an external source can
only flow into the unit. This
allows the unit to operate
whenever DC power is correctly
applied to either or both of the two
inputs.
C4.0
FEATURES AND BENEFITS OF THE DUAL-SOURCE DESIGN
a) The Switch unit can receive power from either input, “A” or “B”. The hub will
normally draw its power from the DC source with the highest voltage at a given
time.
b) The Switch unit will not allow power to flow from a higher voltage input to a lower
voltage input, i.e. the two DC power sources are not mixed together by the hub.
c) When one correct DC input is present, the Switch will receive power if the other DC
input is absent, or even if it is connected with reverse polarity or shorted or
grounded.
d) Reverse polarity connections, if they should accidentally occur on either input, will
not damage the Switch or power supply internally (nor will it blow the fuse in the
internal power supply) because of the blocking action of the diodes. This is true
even if one input connection is reversed while the Switch is operating from the other
source.
e)
The Switch will not receive power (and will not work) when both inputs are
simultaneously absent or are both incorrectly connected.
Figure C5.0: DC Dual-Source, wiring
connections with Dual-Source option.
Dual Source Terminal block
C5.0 INSTALLATION
This section describes the proper connection of the -48VDC, 12VDC, 24VDC,
125VDC and 250VDC dual source leads to the power terminal block on the Magnum
6KQE Switch (shown in Figure above)