GarrettCom 6K25 User Manual
Page 66
Magnum 6K25 Managed Fiber Switch Installation and User Guide (04/06)
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The functionality of the Magnum 6K25 Switch -48VDC, 24VDC and 125VDC
Dual-Source Option units is identical to the standard AC-powered models. Refer to the
main sections of this Installation and User Guide for a detailed description of the
Magnum 6K25 Switches.
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.
C5.0 INSTALLATION
This section describes the proper connection of the -48VDC, 24VDC and
125VDC dual source leads to the -48VDC, 24VDC 7 125VDC power terminal block on
the Magnum 6Ks Switch (shown in Figure )
The -48VDC terminal block on the Magnum 6K25 Switch, as shown in Fig C5.0 is
located on the right rear of the unit and
is equipped with five (5) screw-down
lead posts. If it is the reverse model it
is located on the left rear. The primary
terminals are identified as positive
(A+), negative (A-), and the secondary
power terminals as negative (B-),
positive(B+). The chassis “earth” or ground (GND) is a threaded post with a #6 nut. The
Dual Source terminal block for the 24VDC and 125VDC are similar.
Figure C5.0: -48VDC Dual-Source, wiring connections to the External
Terminal Block on a Magnum 48VDC with Dual-Source option
Note: The GND should be hooked up first. The 6K25 unit has a floating ground, so the
36-70VDC
GND
A+ A- B- B+
36-70VDC
GND
FUSE
+
-
SUPPLY
A+
A-
B-
B+
GND
CHASSIS
HUB