Cisco WS-C2950-24 Installation Manual page 111

Chapter 3 Installing and Connecting the Router
Figure 3-31
In Figure
Figure 3-32
In Figure
is allowed only if Va equals Vb (within 0.25 V).
If source A and source B are wired with common positive terminals and their voltages are unequal by
Caution
more than 0.25 V, the higher-voltage source can discharge into the lower-voltage source through the
negative terminals. Excessive discharging currents through these terminals can actuate one or both of the
dual- input DC power supply's internal A- or B- fuses, resulting in lack of redundancy or system failure.
When source A and source B are within 0.25 V, discharge current is minimal.
When source A and source B are wired with common negative terminals, as in
Note
does not occur and there is no requirement that source A and source B voltages be equal.
OL-18712-01
Connecting to One Source Only—Source A or Source B
3-32, source A and source B share common negative terminal connections.
Connecting Source A and Source B with Common Negative Terminals
3-33, source A and source B share common positive terminal connections. This configuration
Cisco 2900 and 3900 Series Hardware Installation
Connecting Power
Figure 3-32, discharging
3-29