What is USB and will it play a role in the 21st century?

These days new PCs are equipped for USB, but what is USB and what can it do for me? Well, let`s try to answer a few questions.

Universal Serial Bus (USB) technology allows you to install computer peripherals without using dedicated computer slots or cards for each device and the beauty of the technology is that it is plug and play all the way. It basically takes plug and play of computer peripherals outside the box without reconfiguring the system.

PCs equipped with USB will automatically allow computer devices to be recognised and configured as soon as you attached them to your PC. You don`t even have to reboot or run setup and when a device is added or removed from your PC, USB will detect it and automatically add or remove the driver software.

USB also allows up to 127 multiple devices to run simultaneously on a computer, with peripherals such as monitors and keyboards acting as additional plug-in sites, or hubs.

It`s as easy as plugging in a lamp into the wall and switching it on and off.

You don`t even need special software to run USB, because the latest Windows operating systems are already equipped with USB recognition.

Hopefully, in the near future, you will not need to purchase or install additional software for each new peripheral. However, new peripheral products (including those never-before-seen) may mean a gap between the peripheral availability and software upgrades. This may mean you receive a diskette with your new USB peripheral with the updated driver information.

Frequently asked questions about USB:

Q1: How long of a cable can I use to connect my device?
A1: In practice, the USB specification limits the length of a cable between full speed devices to 5 meters (a little under 16 feet 5 inches). For a low speed device the limit is 3 meters (9 feet 10 inches).

Q2: Why can`t I use a cable longer than 3 or 5m?
A2: USB`s electrical design doesn`t allow it. When USB was designed, a decision was made to handle the propagation of electromagnetic fields on USB data lines in a way that limited the maximum length of a USB cable to something in the range of 4m. This method has a number of advantages and, since USB is intended for a desktop environment, the range limitations were deemed acceptable.

Q3: How far away from a PC can I put a USB device?
A3: With the maximum of 5 hubs connected with 5m cables and a 5m cable going to your full speed device, this will give you 30m of cable With a low speed device, you will be able to get a range up to 27m, depending on how long the device`s cable is. With a straightforward cable route, you will probably be able to reach out 25m or so from the PC.

Q4: I need to put a USB device X distance from my PC. What do I do?
A4: If X is less than 25m or so (see previous question), buy a bunch of hubs and connect them serially with 5m cables. If you need to go farther than that, put another PC, or maybe a laptop, out where you need the device to be and network it with the first PC using something that`s intended to be a long-range connection, such as Ethernet or RS-485. If you need to use nothing but USB, consider using USB based Ethernet adapters to hook the PCs together.

Q5: How can I connect two PCs to each other with USB?
A5: You need a specialized USB peripheral known as a USB bridge (sometimes called a USB to USB adapter) to do this. Anchor Chips and e-Tek labs, among others, make USB bridges.

Q6: You mean I can`t make a direct cable connection like a null modem?
A6: Correct. In fact, if you try this with an illegal A to A USB cable, you`ll short the two PCs` power supplies together, possibly destroying one or both machines or causing a fire hazard. Even there were no danger to the machines from the problem with two power supplies, there still wouldn`t be any way to get the two PCs talking to each other, since USB doesn`t support that particular kind of communication. A reasonably priced solution to handle this need is the USB bridge.

Q7: So why do people make A to A cables, anyway? What kinds of cables do I need to connect USB devices together?
A7: A number of cable vendors seem to have reached the conclusion that USB is like a PC`s serial port, only faster, so you need all sorts of special hardware to create the USB connection you need to make. This is completely incorrect. The only kind of cables you`ll ever need to connect normal USB products are A to B cables of various lengths. Some special kinds of devices use nonstandard connectors and so come with their own special cable.