Cisco SE2800 Quick Start Guide - Page 24
Approved Scenarios and Scenarios Not Approved for Dual DC Power Supply Configuration,
View all Cisco SE2800 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 24 highlights
Approved Scenarios and Scenarios Not Approved for Dual DC Power Supply Configuration You can connect a single DC power source to either the A input or the B input. If there are dual power sources, connect one source to the A input and one source to the B input. Both sources must be the same polarity (with respect to ground) and voltage (within 0.25 volts). Do not connect -DC grounded and +DC grounded dual sources to Cisco 2811, Cisco 2821, and Cisco 2851 series integrated services routers. Caution Dual sources with opposite-polarity grounding damage equipment. In Figure 21, either the positive source terminal or the negative source terminal is tied to ground. Figure 21 Connecting to One Source Only-Source A or Source B A- A- + + A+ A+ B+ B+ 127037 B- B- In Figure 22, source A and source B share common negative terminal connections. Figure 22 Connecting Source A and Source B with Common Negative Terminals AVa + A+ + B+ Vb B- 127039 In Figure 23, source A and source B share common positive terminal connections. This is allowed only if Va equals Vb (within 0.25 V). Caution When connecting source A and source B with common positive terminals, if source A and source B voltages are unequal by more than 0.25 V, the higher-voltage source can discharge into the lower-voltage source through the Aand B- input terminals. Excessive discharging currents through these terminals can cause one or both of the dual input DC power supply's internal A- or B- fuses to open, resulting in lack of redundancy or system failure. When source A and source B are within 0.25 V, discharge current is minimal. 24