Fans, Ventilation, And Airflow - Cisco 2900 Series Installation Manual

Hardware Features
Software Features
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Fans, Ventilation, and Airflow

The Cisco 2911 and Cisco 3900 series ISRs have optional fan filters that are easy to replace. The filters
may be used to meet Network Equipment Building Systems (NEBS) requirements, or to operate in dusty
environments. When a filter becomes dirty, discard it and replace it with a new one. See the
a Fan Tray or Air Filter" section on page
Fan speeds are controlled by the fan speed controller circuitry. To minimize noise, the fans operate at
one of several predetermined speeds and are dependent on the input ambient air temperature.
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Figure 1-19
Figure 1-20
Cisco 2900 Series and 3900 Series Hardware Installation Guide
1-26
See the Configuring Power Efficiency Management module in the Cisco 3900 Series, 2900 Series,
and 1900 Series Integrated Services Routers Software Configuration Guide at Cisco.com. Learn
how to configure and manage power going to modules and peripherals.
Figure 1-19 shows Cisco 2901 airflow.
Figure 1-20 shows Cisco 2911 airflow.
Figure 1-21 shows Cisco 2921 and 2951 airflow.
Figure 1-22 shows the Cisco 3900 series standard (non NEBS) airflow configuration. For NEBS, the
airflow is reversed.
Figure 1-23 shows the Cisco 3900 series standard NEBS airflow configuration.
Cisco 2901 Router Airflow
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Cisco 2911 Router Airflow
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Chapter 1 Overview of the Routers
"Replacing
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