CISSP考试指南笔记：3.23 内部支持系统

Electric Power

Power Protection

Protecting power can be done in three ways: through UPSs, power line conditioners, and backup sources.

Online UPS systems use AC line voltage to charge a bank of batteries. Standby UPS devices stay inactive until a power line fails.

Backup power supplies are necessary when there is a power failure and the outage will last longer than a UPS can last.

An alternative power source should be tested periodically to make sure it works and to the extent expected.

Electric Power Issues

When clean power is being provided, the power supply contains no interference or voltage fluctuation. The possible types of interference (line noise) are electromagnetic interference (EMI) and radio frequency interference (RFI), which can cause disturbance to the flow of electric power while it travels across a power line.

Interference interrupts the flow of an electrical current, and fluctuations can actually deliver a different level of voltage than what was expected.

The following explains the different types of voltage fluctuations possible with electric power:

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