Dell E5420M, E5520M manual Back View

9.	microphone	17.	touchpad buttons (2)
10.	volume control buttons	18.	wireless switch
11.	optical-drive eject button	19.	power and battery status indicators
12.	optical drive	20.	trackstick buttons (3)
13.	USB 2.0 connector	21.	trackstick (optional)
14.	headphone connector	22.	keyboard
15.	fingerprint reader (optional)	23.	device status lights
16.	touchpad

Figure 2. Back View
1.	network connector	7.	IEEE 1394 connector
2.	USB 2.0 connector	8.	HDMI connector
3.	modem connector (optional)	9.	e-SATA/USB 2.0 connector
4.	power connector	10.	USB 2.0 connector
5.	security cable slot	11.	Secure Digital (SD) card slot
6.	cooling vent	12.	ExpressCard slot

WARNING: Do not block, push objects into, or allow dust to accumulate in the air vents. Do not store your Dell computer in a low-airflow environment, such as a closed briefcase, while it is running. Restricting the airflow can damage the computer or cause a fire. The computer turns on the fan when the computer gets hot. Fan noise is normal and does not indicate a problem with the fan or the computer.

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