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What is USB? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Is USB?

USB Short for Universal Serial Bus, an external bus standard that

supports data transfer rates of 12 Mbps.

Today just about every PC comes with Universal Serial Bus, or USB

ports. In fact, many computers will even have additional USB ports

located on the front of the tower, in additional to two standard USB ports

at the back. In the late 1990s, a few computer manufacturers started

including USB support in their new systems, but today USB has become

a standard connection port for many devices such as keyboards, mice,

joysticks and digital cameras to name but a few USB-enabled devices.

USB is able to support and is supported by a large range of products.

Adding to the appeal of USB is that it is supported at the operating

system level, and compared to alternative ports such as parallel or serial

ports, USB is very user-friendly. When USB first started appearing in the

marketplace, it was (and still is) referred to as a plug-and-play port

because of its ease of use. Consumers without a lot of technical or

hardware knowledge were able to easily connect USB devices to their

computer. You no longer needed to turn the computer off to install the

devices either. You simply plug them in and go. USB devices can also be

used across multiple platforms. USB works on Windows and Mac, plus

can be used with other operating systems, such as Linux, for example,

with a reliable degree of success.

Before USB, connecting devices to your system was often a hassle.

Modems and digital cameras were connected via the serial port which

was quite slow, as only 1 bit is transmitted at a time through a serial port.

While printers generally required a parallel printer port, which is able to

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What is USB? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

receive more than one bit at a time — that is, it receives several bits in

parallel. Most systems provided two serial ports and a parallel printer

port. If you had several devices, unhooking one device and setting up the

software and drivers to use another device could often be problematic for

the user.

The introduction of USB ended many of the headaches associated with

needing to use serial ports and parallel printer ports. USB offered

consumers the option to connect up to 127 devices, either directly or

through the use of a USB hub. It was much faster since USB supports

data transfer rates of 12 Mbps for disk drives and other high-speed

throughput and 1.5Mbps for devices that need less bandwidth.

Additionally, consumers can literally plug almost any USB device into

their computer, and Windows will detect it and automatically set-up the

hardware settings for the device. Once that device has been installed you

can remove it from your system and the next time you plug it in,

Windows will automatically detect it.

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What is USB? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Types of USB

USB 1x

First released in 1996, the original USB 1.0 standard offered data rates of

1.5 Mbps. The USB 1.1 standard followed with two data rates: 12 Mbps

for devices such as disk drives that need high-speed throughput and 1.5

Mbps for devices such as joysticks that need much less bandwidth.

USB 2x

In 2002 a newer specification USB 2.0, also called Hi-Speed USB 2.0,

was introduced. It increased the data transfer rate for PC to USB device to

480 Mbps, which is 40 times faster than the USB 1.1 specification. With

the increased bandwidth, high throughput peripherals such as digital

cameras, CD burners and video equipment could now be connected with

USB. It also allowed for multiple high-speed devices to run

simultaneously. Another important feature of USB 2.0 is that it supports

Windows XP through Windows update.

USB OTG

Short for USB On-The-Go, an extension of the USB 2.0 specification for

connecting peripheral devices to each other. USB OTG products can

communicate with each other without the need to be connected to a PC.

USB OTG addresses the need for devices to communicate directly for

mobile connectivity. USB OTG allows consumers to connect mobile

devices without a PC. For example, USB OTG lets consumers plug their

digital camera directly into a compliant printer and print directly from the

camera, removing the need to go through the computer. Similarly, a PDA

keyboard with a USB OTG interface can communicate with any brand

PDA that has a USB OTG interface.

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USB-OTG also provides limited host capability to communicate with

selected other USB peripherals, a small USB connector to fit the mobile

form factor and low power features to preserve battery life. USB OTG is

a supplement to the USB 2.0 specification.

Types of USB Connectors

Currently, there are four types of USB connectors: Type A, Type B, mini-

A and mini-B and are supported by the different USB specifications

(USB 1, USB 2 and USB-OTG).

USB A (Host)

Often referred to as the downstream connector, the Type A USB

connector is rectangular in shape and is the one you use to plug into the

CPU or USB hub.

USB B (Device)

Also called the upstream connector, the Type B USB connector is more

box-shaped and is the end that attaches directly to the device (such as a

printer or digital camera).

USB 1.1 specifies the Type A and Type B.

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Mini-B

The USB 2.0 connector was too large for many of the new handheld

devices, such as PDAs and cell phones. The mini-B was introduced to

enable consumers to take advantage of USB PC connectivity for these

smaller devices.

USB 2.0 specifies the Type A, Type B and mini-B.

Mini-A

With the need to connect mobile devices without the aid of a computer,

the mini-A port was designed to connect the new generation of smaller

mobile devices.

USB OTG specifies the mini-A.

Certified Wireless USB

With an estimated 2 billion plus USB connected devices in the world and