Cisco 2900 Series Installation Manual page 105

Chapter 3 Installing and Connecting the Router
Figure 3-22
Approved Scenarios and Scenarios Not Approved for Dual DC Power Supply Configuration on Cisco
2911, 2921, and 2951 Routers
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 2911, Cisco 2921, and Cisco 2951 routers.
Dual sources with opposite-polarity grounding damage equipment.
Caution
In Figure
Figure 3-23
Wire Routing and Attachment for Cisco 2921 and Cisco 2951 Routers
Plastic covers
3-23, either the positive source terminal or the negative source terminal is tied to ground.
Connecting to One Source Only—Source A or Source B
Battery
Source
+
G N D
-
+
+
-
Battery
Source
A-
+
A+
B+
B-
Cisco 2900 and 3900 Series Hardware Installation
Connecting Power
Cable tie
From DC
power
source
A-
A+
B+
B-
3-23