Dell Studio 1558 (Early 2010) - Manual (Page 313)

Ports
313
Ports
USB Port
The Universal Serial Bus (USB) is an external bus standard that supports data
transfer rates of 480 Mbps in case of USB 2.0. USB gives you a single,
standardized way to connect many devices to your computer. USB also
supports Plug-and-Play installation and hot swapping.
The USB standard uses A and B connectors to avoid confusion:
• Connectors A head upstream toward the computer.
• Connectors B head downstream and connect to individual devices.
Pin Signal
1 USB5V+
2 USBP–
3 USBP+
4 GND