Something about USB
Results of some ten years ago, the rear panel of the system block any PC «decorated» wide variety of connectors. In that distant time when computer technology was just beginning to develop, for each device there was a special connection interface: COM-port – mouse, DIN-connector – keyboard, parallel port – Printer …
With the advent of USB (Universal Serial Bus) everything became much easier. At this interface went still and video cameras, keyboards, IFIs and lots of other peripheral devices. But not all USB identical: differences in standards, data rates and even in the form factor connectors are capable of thorough sow confusion in the minds of inexperienced users. We will help bring clarity and understanding, «who is who» in the realm of USB.
Benefits of USB
Today USB replaced virtually all other interfaces for connecting computer peripherals (see sidebar «External interfaces – competitors USB»), which were key to his undeniable advantages.
■ Prevalence. Any computer, released in recent years, is equipped with one or more ports of USB (in today’s desktop PC to up to 12, in the vast majority of laptops – 3-4). In contrast, the USB-devices is great.
■ Easy to use. USB – the perfect embodiment of the principle of Plug and Play. Devices with this interface can be connected and disconnected while the computer. Modern operating systems immediately recognize a USB-device and loads the necessary drivers. On many computers, to improve convenience and access USB ports located on the front or the side of the shell. Also confused connectors and can not be wrong to connect peripherals..
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■ High throughput. At the USB 2.0 interface, it is 480 Mbps. Copying a file size of 700 MB on the drive connected to port USB, will take no more than 20 seconds ■ Ensuring food. USB port not only serves to connect the periphery, but can «feed» gadgets with low power consumption, for example, mice, keyboards, flash drives and even 2.5-inch hard drives. Power supply from the USB bus is 5 V at a current of up to 500 mA. This, of course, is not enough for peripheral devices with a relatively high power consumption, such as printers or external hard drives form factor of 3.5. Therefore, they are equipped with its own power supply, plug directly into a wall outlet.
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Simple and easy
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Central hub for all USB-devices is the computer. Only with him, they can «talk» directly. This connection is called «Point to Point». The first USB-connected device is automatically detected by the operating system, after which she searches for the correct driver. This is the rule: the newer version of the operating system, the greater the likelihood that the user does not have to install the driver yourself. For example, Windows XP and Vista will automatically recognize USB flash drives, card readers and external hard drives and register them as removable drives. . Necessary for these devices drivers are included in the distribution of Windows and are always «hand» in the system. Windows Vista to the same shall have additional drivers for most popular printers, scanners, gaming keyboards and other devices. |
COUNCIL
If Windows does not itself determine the connected USB-device driver for it would have to set yourself (as a rule, it can be found on the disk supplied with your USB-devices). Having bought the printer or MFP with USB, do not rush immediately connect it: first look in the manual and learn how to install in order to understand whether you need to install the software or available in the OS will be enough. Otherwise, Windows may install the driver with a smaller set of functions or even recognize the device incorrectly.
With rare exception, USB-gadgets can communicate with each other only through the computer. В этом случае ПК играет роль так называемого USB-хоста. In this case, the PC plays the role of the so-called USB-host. He asks each device connected to USB and called the client, information about the availability of necessary data, then organizes the «Dialogue». Transfer files «on their own initiative» clients is prohibited. This method, called the poll, while consuming system resources, but makes possible the creation of simple and, as a consequence, low-cost USB-devices.
Types of USB-connector
■ There are two types of connectors and plug USB: Type A is used to connect USB-devices to laptops and desktop computers. Connector type B USB-equipped peripheral devices. There are several variants of the connector of the second type: In fact, Mini-B and Micro-V.
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Type A Type A connector connects to a USB-type connector on the computer or a USB-hub. Some printers and multifunction devices are also equipped with plug type A – for connecting cameras. |
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Type B Connector Type B is connected to the corresponding USB-connector, which are usually equipped with large peripheral devices, such as the IFIs, printers and scanners. |
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Mini-USB (type B) USB-device more modest size, such as digital cameras, PDAs or cell phones, equipped with a miniature version of the plug-type, called the Mini-USB (or, more correctly, Mini-B). |
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Micro-USB (type B) There is a USB-connector more compact than the Mini-V – a slot Micro-B. They often boast mobile phones. |
Direct connection of two USB-gadgets possible with the help of technology On-The-Go. Its use will allow to print pictures without the mediation of a computer or directly to share music files between MP3-players.
Benefits competitors
Interfaces USB, eSATA and FireWire differ from each other primarily on the speed of data transmission (see box «Capacity USB, eSATA and FireWire compared»).
USB External interfaces – USB competitors:
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FireWire interface for connecting camcorders and external hard drives. . Standard FireWire 800 provides work at higher speeds than standard USB 2.0, but today it is losing its relevance. |
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SATA and eSATA interface Along with SATA, used to connect internal hard drives, there is eSATA for connecting external disk drives. Data on eSATA carried almost four times faster than USB 2.0. Perhaps, eSATA – the only interface that has a clear advantage over USB and not going to surrender position. |
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PS / 2 This once-standard interface for connecting input devices with the advent of USB is gradually disappearing. Purple PS / 2 connector is traditionally designed for keyboard, green – for the mouse. |
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Parallel port Before the USB has been widely distributed, parallel port was a traditional interface for connecting printers and scanners. Now he is becoming increasingly rare. |
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The game port (MIDI-port) to the game port previously connected a joystick or MIDI-keyboard music. Today, such devices are used to connect USB-connector, so that the MIDI-ports rare. |
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Serial port Serial port (COM port), which was previously connected a mouse and a modem today at the home PC absolutely useless. This interface is used in industry – for the management of special machines. |
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External SCSI-interface is used, along with common today external hard drives with interface IDE, often used drives with an interface SCSI, which are now valid only for server systems. |
■ FireWire serves primarily to connect to a PC video cameras and some models of hard drives. Actual version of FireWire 800, significantly faster than the USB 2.0 (800 against 480 Mbit / s). But the device with the Fire Wire interface is usually more expensive than those with USB.
■ eSATA is used to connect external hard drives, and more recently – and some models of flash drives. Unlike USB and FireWire, external hard drive with eSATA interface does not require conversion of data, which excludes the additional link, the inhibitory interaction with the PC. Therefore, the rate for such hard drives at the level of built-in computer hard drives. If you need maximum performance peripherals, the eSATA – the best solution.
Capacity USB, eSATA and FireWire versus
If you plan to buy an external hard drive, then you have to choose one of several possible interfaces to connect to have a different capacity: the highest data rate provides eSATA, FireWire 800 is followed and the race closes USB 2.0. But the latter has its trump card: the USB connector is present on any computer.
The prevailing balance of power will change the output devices with interface USB 3.0, which will be the fastest interface data transfer. But until the new USB standard will be widespread, it will take time.
USB Standards
■ USB 1.1 Computers that were released before 2002, make available to the user interface USB 1.1. Data for this standard is carried out slowly. The theoretical peak bandwidth of 12 Mbps (or 1.5 Mb / s). Input devices – keyboard and mouse – this is quite enough.
Note. An earlier version, USB 1.0, did not get distribution, and remained on paper. Finished products corresponding to this standard, the market is not received.
■ USB 2.0. Computers and laptops that were released after 2003, as a rule, are equipped with ports USB 2.0. Maximum speed in comparison with the standard 1.1 markedly increased to 480 Mbps (or 60 MB / s). Although in practice to achieve this level of bandwidth can not.
Higher throughput devices provide USB 2.0, marked with the logo «USB 2.0 Hi-Speed». If on the box or package the device indicated «USB 2.0 Full-Speed», which means that data will be transmitted at the speed of standard USB 1.1.
«Slow motion»
If Windows does not itself determine the connected USB-device driver for it would have to set yourself (as a rule, it can be found on the disk supplied with your USB-devices). Having bought the printer or MFP with USB, do not rush immediately connect it: first look at the manual and learn how to install in order to understand whether you need to install the software or available in the OS will be sufficient. Otherwise, Windows may install the driver with a smaller set of functions or even recognize the device incorrectly.
How to increase the number of USB-ports
The easiest way to do this using the so-called USB-hubs (USB-hubs). These small «boxes» is available at a price of 100 rubles. Occupying just one USB-slot machine, this device provides a return, as a rule, four (or more) port. Theoretically, the use of USB-hub can connect to one computer to 127 devices to USB.
Another advantage of USB-hub lies in the fact that it can be installed in a convenient place for you. This would obviate the need each time to climb under the computer table to find the right port to connect USB-connector. In addition, if you connect the device lacks the length of USB-cable, the hub can act as an extender.
It should be noted that there are two types of hubs.
■ Active. As a source of electricity it uses a separate power supply that shipped with your hub. . USB-ports of the hub are able to provide the maximum for this interface amperage, so to active hubs can be connected even such «hungry» devices as external hard drives.
■ Passive. Meals served with him on the USB-port of the PC and is divided between all ports, so passive hubs are suitable only for connecting devices with low power consumption.
USB Network
Mains USB-Hub Belkin Components allows you to connect up to five USB-devices that will interact with the computer on the network. With WLAN-router can be arranged for them a wireless connection. Alternative to the hub can be considered expansion card installed in PCI slot motherboard PC. When using it you’ll have a few extra connectors USB (usually four). Such boards can be purchased at a price of 300 rubles. Disadvantage: Additional USB ports are located on the rear of the system unit.
What is the maximum length of USB cable
The maximum length of a standard USB cable is 5 meters. If this is not enough to require specialized extenders (after each 5-meter area is needed is a relay with independent power supply, in the role which, incidentally, can act and USB-Hub). It means you can reach the length of connection, equal to 25 meters. Using the so-called USB Line Extender (cost 1000 rubles. And more, this device is a USB-adapter and hub, which are connected by standard network cable) will overcome the distance and 60 meters.
What do the logos USB
The packaging of most USB-devices decorate one or more of the following logos. Their presence indicates that the device meets the technical requirements described in the specifications and documents nonprofit USB Implementers Forum. If you find a symbol that is not in our list, be careful: you may be dealing with low-grade products «third-party», which may not support the claimed characteristics.
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USB symbol This symbol is allowed to apply to all devices with USB. It only indicates that the device connects to a specific port. |
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USB This symbol is found on early models of USB-devices. In modern production, he is no longer used. |
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USB 1.1 A typical symbol USB. He informs that this USB device has passed the official certification. Such a device can operate at speeds of Full Speed (12 Mbits / s). |
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On-The-Go In 2001, the USB symbol was added to the green signature «On-The-Go». Devices marked with this sign, can communicate without the mediation of the computer. |
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USB 2.0 Hi-Speed This symbol is applied to the device certified for the standard USB Hi-Speed. The data is transferred by them to the maximum possible for the standard USB 2.0 speed (up to 480 Mbit / s). |
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USB 2.0 Hi-Speed On-The-Go this symbol may be marked only devices operating at very high speed and supporting technology On-The-Go. |
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Wireless USB is currently in such a logo means a very small number of devices. They are able to transfer data wirelessly at speeds up to 480 Mbps. |
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USB 3.0 devices with the logo will appear on the market until next year. They will have a new, faster interface. |
Power consumption: USB-devices
Many USB-devices for enough food, obtained by interface USB, so they do not need a connector for an electrical outlet.
Depending on the level of energy consumption, USB-devices are divided into two groups:
■ Low-power: consumes less than 100 mA.
■ High-power : допустимый верхний предел для устройств класса high-power – 500 мАfor the device class of high-power – 500 mA. They are recommended to connect directly to a computer or to an active hub. When connected to a passive hub of high-power devices will not work, what you will be warned the message of Windows.
USB-acceleration
Different standards have USB tremendous difference in throughput. High-speed hard drive capacity can be fully utilized only with USB 3.0.
About Wireless USB
Wireless USB – a new standard designed to enable a wireless connection on the bus USB. Infinite wire on and under the table safely be left on and under the table safely be left in the past, if printers, scanners, external hard drives and MP3-players were able to communicate with a computer without using a cable. This new technology offered by USB Imple menters Forum, will help realize this dream.
The new USB-cable
«Traditional» USB-cable consists of four wires. . Two of them carry data, the other two are used for power supply. For the new high-speed mode of USB version 3.0, the four wires is not enough, so the new cable will have four additional lines of data: the first pair will serve for the reception, the second – for the transfer. The advantage: unlike USB 2.0 transmission and reception of data will be carried out simultaneously and at maximum speed. USB 3.0 cable will be equipped with a new connector with five additional contacts.
As an example, consider how you can simultaneously connect a regular USB-printer and scanner, using Wireless USB. Not without wires in this case do not succeed all the same: both devices have to connect the cables with wireless USB-hub, which is «in their name» will communicate with the computer. At the same time in the PC must be set appropriate wireless USB-adapter. In this case, printer and scanner will be determined by the system as the devices connected to the computer in the traditional way.
It should take into account the fact that the maximum transfer rate of 480 Mbps Wireless USB interface provides only if the distance between the hub and the computer does not exceed three meters. At a greater distance Wireless USB throughput is reduced. If the way wireless communication channel to meet obstacles such as walls, data transmission will be impossible.
Note. Alternative solutions Wireless USB are USB-hubs, connected to the LAN. They can connect to the WLAN-router, thereby also becomes possible to wirelessly connect USB-devices and computer.
New USB 3.0
Standard USB 3.0 was a further development for USB 2.0, bringing to it a number of improvements.
■ Throughput. In fact, USB 2.0 provides data transfer at maximum speed, barely exceeding 30 MB / sec. This limits the ability of many devices, especially external disk drives that can operate at speeds greater than indicated by 2-4 times. In USB 3.0 throughput will increase in 10 times, reaching the level of 5 Gbit / sec. For this purpose, USB 3.0 is equipped with more sophisticated technology, data transmission, in which to broadcast a single byte is not required, 8 and 10 bits. Therefore, the actual speed limit data transfer of approximately 500 MB / sec. However, even these results will hardly be able to achieve – a stumbling block will be the speed capabilities of external devices (the same drive), which speeds lag far behind the capabilities of USB 3.0.
■ Joints. One of the major challenges facing the developers of the new standard – the preservation of compatibility connectors USB 3.0 and 2.0. As a result, you can easily connect the device to a USB 2.0 connector USB 3.0. But to anyone who aspires to maximum speed, still have to buy new cables (see sidebar «New USB-cable»). They are arranged more complicated and will cost more than similar cables are USB 2.0. In addition, not all types of connectors will be backward-compatible with the old standard USB 2.0. If in the case of type A USB connector can afford to be a little blood, «write-» five new contacts in the connectors already available, then with the USB connector type B, and especially Micro-B, everything was much more complicated. In this case, had to change the constructive connector, in effect dividing it into two parts: first – to maintain compatibility with the “Previous standards, pre submits an« old »Port USB 2.0, the second – brings together five new lines have appeared in USB 3.0. Thus, these types of connectors can not be connected to port USB 2.0.
■ Meals. USB 3.0 connectors supports greater amperage than any previous version of USB: 900 instead of the previous 500 mA. This is important, for example, when using external hard drives.
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■ Energy. In the USB 2.0 host had to continuously poll the connected devices, finding out whether they have a new batch of data, so they all had to be constantly active. Denial of such a cyclical survey in USB 3.0 will use the power saving mode.
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