Cisco Systems 3800 Series warranty Connecting to One Source Only-Source a or Source B

Power Connections

Caution Dual sources with opposite-polarity grounding damage equipment.

In Figure 16, either the positive source terminal or the negative source terminal is tied to ground.

Figure 16 Connecting to One Source Only—Source A or Source B

A-	A-
+	+
A+	A+

B+	B+
B-	B-	127037

In Figure 17, source A and source B share common negative terminal connections.

Figure 17 Connecting Source A and Source B with Common Negative Terminals

Va

+

+

Vb

A-

A+

B+

B-

127039

In Figure 18, source A and source B share common positive terminal connections. This configuration is allowed only if Va equals Vb (within 0.25 V).

Caution If source A and source B are wired with common positive terminals and their voltages are unequal by 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.

Connecting Cables to Cisco 3800 Series Routers

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