To let your computer sleep but remain available to answer the modem, select the checkbox labeled “Wake when the modem detects a ring.” You might select this option if you use your computer to receive faxes.

To let your computer sleep but remain available to network administrator access, select the checkbox labeled “Wake for Ethernet network administrator access.” If you select this option, an administrator can send a Wake-on-LAN packet to wake the computer. Using the “ssh” or “telnet” Terminal commands will not wake the computer.

To put your computer to sleep by pressing the power button once, select the checkbox labeled “Allow power button to sleep the computer.”

To reduce the brightness of the display while using the battery, select the checkbox labeled “Reduce the brightness of the built-in display when using this power source.” This dims the display slightly to save energy but you can continue to work.

To reduce the brightness of the display automatically before the display goes to sleep, select the checkbox labeled “Automatically reduce the brightness of the display before the display sleeps.”

To make your computer start up automatically after a power interruption, select the checkbox labeled “Restart automatically after a power failure.”

To save energy by causing your computer to work more slowly, choose Reduced from the Processor Performance pop-up menu. Choosing Highest lets your computer work at its fastest but uses more energy.

Some models support the Automatic setting, which allows your computer to switch rapidly back and forth between the Highest and Reduced settings to optimize energy use, depending on how much work the processor is doing.