Cisco 3845 Quick Start Guide - Page 22

Figure 18 Connecting Source A and Source B with Common Positive Terminals Va voltage = Vb voltage (greater than 0.25 V) Va voltage = Vb voltage (within 0.25 V) AVa + A+ AVa + A+ + B+ Vb B- + B+ Vb B- 127040 In Figure 19, source A and source B are wired with opposite polarity grounds. Do not use this configuration. Caution Do not use the DC input configuration shown in Figure 19. Figure 19 Source A and Source B Wired with Opposite-Polarity Grounds AVa + A+ + B+ Vb B- 127041 Connecting the Router to Backup Power The Cisco 3845 router operates in redundant mode when two power supplies are installed. The Cisco 3825 router has one internal power supply and a connector for mating to an external backup power source. To connect the Cisco 3825 router to the external Cisco Redundant Power System (RPS), remove the RPS connector cover from the bezel and connect the RPS cable. (See Figure 20 and Figure 21.) See the Cisco RPS-675 Hardware Installation Guide for more information about RPS power connections. To locate this documents, see the "Where to Go Next" section on page 34. 22