GarrettCom DS 880 - Manual (Page 31)

Magnum DS880 Dual-Speed Stackable Hubs Installation and User Guide (05/01)
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APPENDIX B : Optional 48V DC Power Supply, Addendum
B1.0
SPECIFICATIONS - FOR DUAL-SPEED DS880 HUBS
Power Supply (Internal 48 VDC Option)
DC Power Connector: 3 terminals: “ - “, “GND”, “+”
Input Voltage: 36 - 70 VDC (auto-ranging)
Power Consumption: Model DS880: 12 watt typical, 20 watts max.
With the exception of the power supply, all specifications and functions of
Magnum DS880-48VDC models are identical to those listed in Section 1.
B2.0 48V DC SOURCE OPTION, THEORY OF OPERATION
The 48VDC power option is designed using diodes inside on each DC power input
line behind the two external power connection terminals, so that the power from an external
source can only flow into the hub. This
allows the hub to operate only whenever
DC power is correctly applied to the two
inputs. It protects the hub from incorrect
DC input connections. An incorrect
polarity connection, for example, will neither effect the hub, nor its power supply internally, nor
will it blow the fuse in the internal power supply.
A+
A-
GND
GND
CHASSIS
FUSE
+
-
SUPPLY
HUB
POWER SWITCH
The power switch (included on premium-priced NEBS-certified units only) is used for
powering the hub on and off when it is placed into or taken out of service.
B3.0 APPLICATIONS
Magnum DS880 Dual-Speed Hubs are easily installed in a variety of applications
where 48 VDC power is used as the primary power source. The 48VDC power configuration
provides an Ethernet networking solution utilizing a special power supply in hubs with a proven
track record.
The solution is particularly useful in the telecommunication industry, where it is
common for facilities to operate on 48VDC power. Such companies include regular and wireless
telephone service providers, Internet Service Providers (ISPs) and other communication
companies. In addition, many high availability equipment services, such as broadcasters,
publishers, newspaper operations, brokerage firms and other facilities often use a battery backup
system to maintain operations in the event of a power failure. It is also frequently used for
computer system backup, management and operations monitoring equipment.