USB : Computer Hardware Buyers’ Glossary

USB (Universal Serial Bus). A way of connecting several low speed peripherals to a PC (Personal Computer) in a daisy chain. Typical peripherals include keyboards, scanners, mice and digital cameras. It runs at 1 MBit/sec, roughly a tenth the speed of an Ethernet LAN (Local Area Network). It is rated to run at 12 MBits per second, and USB-2 is rated to run at 480 Mbits per second. USB-3 is rated to run at 5 GBits (5000 MBits) per second. USB-3 cables are always blue.

USB has almost completely replaced serial and parallel ports for attaching keyboards, mice, cameras, webcams, and other assorted devices.

You are supposed to be able to just plug in a device and go, without rebooting. However, on Vista, I have found they often don’t work unless you do reboot.

If you plug a USB-2 device into a USB-1 computer port, it will work, but you will get only USB-1 speed.

The big problem with it is you can’t tell at a casual glance which way is up on either the male or female USB connector. The rule of thumb is, insert the connector with the white plastic bar on the male down. I am sure you can think of some obscene mnemonic to help you remember this.

Normally you don’t make your own USB cables. However, pre-built cables are expensive, comparable to the cost of much thicker Ethernet cables.

Appearance
Type	USB2-A male connector	USB2-B mini male connector	USB3-A male connector	USB3-B mini male connector
Where Used	Often used on desktop computers.	Often used on printers.	Just becoming common on desktop computers.	Just becoming common on printers.
Orientation	Insert the connector with the white plastic bar on the male down. When the slot is mounted vertically, the white bar goes on the left and the hole on the right. I am sure you can think of some obscene mnemonic or to help you remember this. Put a red dots with Sharpie fine tip permanent marker on the hole side of the cable connectors and on the hole side (top and right) of the slots so you won’t have to think about which way to insert. Just align the red dots.	The rounded part of the D is usually up.	Insert the connector with the blue plastic bar on the male down. When the slot is mounted vertically, the blue bar goes on the left and the hole on the right. Put a red dots with Sharpie fine tip permanent marker on the hole side of the cable connectors and on the hole side (top and right) of the slots so you won’t have to think about which way to insert. Just align the red dots.	The small hump is usually up.