Cisco ASR 9901 Hardware Installation Manual page 41

Preparing for Installation
Figure 50: Cisco ASR 9001 DC Power Source Cabling Scheme for a Single DC Power Module
The color coding of the source DC power cable leads depends on the color coding of the site DC power source.
Because there is no color code standard for source DC wiring, be sure that power source cables are connected
to the power modules using the proper positive (+) and negative (–) polarity:
• In some cases, the source DC cable leads might have a positive (+) or a negative (–) label. This is a
relatively safe indication of the polarity, but you must also verify the polarity by measuring the voltage
between the DC cable leads . Be sure that the positive (+) and negative (–) cable leads match the positive
(+) and negative (–) labels on the power module when making the measurement.
• Green (or green and yellow) cable typically indicates that it is a ground cable.
Caution DC power modules contain reverse voltage protection circuitry to prevent damage to the power module if it
detects a reverse polarity condition. No damage should occur from reverse polarity, but you should correct a
reverse polarity condition immediately.
For a list of the nominal and acceptable value ranges for source DC power, see
Levels, on page 146.
Cisco ASR 9901, ASR 9001, and ASR 9001-S Routers Hardware Installation Guide
DC Powered Router
Power System DC Output
33