|Sunday, 17 September 2006|
USB provides an expandable, hot-pluggable serial interface that ensures a standard, low-cost connection for peripheral devices such as keyboards, mice, joysticks, printers, scanners, storage devices, modems, and the like. The popularity of the USB standard is prominent as most computer manufacturers now include one or more USB interfaces for external USB peripherals as part of their systems. The USB interface has many advantages, such as high speeds, easy connections, plug-and-play (PnP) possible, no need for any external power, supporting many devices, and highly compatible. Therefore, the USB has become a standard port on personal computers. The USB hub provides a convenient central data connection point for attaching multiple peripheral devices to a computer. The hub relays data from the computer to all enabled devices coupled to the data hub, and relays data from the enabled devices to the computer. This data relay is performed without any data storage or significant delay. The USB hub is connected to the computer via a single USB upstream connector. The USB hub also includes a plurality of downstream ports for connecting the peripheral devices to the hub. Taking advantage of this quick connectivity standard are a variety of memory storage apparatus, one of which being a USB flash drive, for example. The USB flash drive is a small memory storage apparatus that interfaces with a host system through a USB connector. The apparatus uses low power non-volatile flash memory as its storage media instead of conventional rotating hard disk media. Without USB, a personal computer requires a separate interface, with specialized electrical, mechanical and software connections, so as to be able to connect to each individual peripheral.
A USB (universal serial bus) system is commonly used in communication products, particularly computers and the related peripheral equipment, for the advantages of higher data transmission speed than earlier RS232 connectors, ease of installation and maintenance. A connector for use in a USB is called a USB connector. Generally the connector is arranged on an electronic device serving as a peripheral device and is able to allow a USB socket that is normally arranged on another peripheral device to be plugged in. Such peripheral devices may include scanners, printers, digital speakers, modems, compact disk drives, radio frequency device transceivers, video/audio links, MP3 players, hard drives, DVD drives, CD drives, smart card/bar code readers, digital cameras, digital video recorders and speaker amplifiers. A USB connector is generally comprised of a connector body, a cable connected to the connector body, and an insulative shell covered on the connector body and a part of the cable to secure the connector body and the cable together. Two different types of USB connectors are in common use. One is a type A connector, which uses a receptacle that contains four pins in a straight line on one side of a connector plate. Another is a type B connector, comprising two pins on either side of the receptacle connector plate. A mini USB connector is much smaller than a standard USB connector and is widely used for connecting a hand-held device, such as a digital camera or a personal digital assistant (PDA) to a computer. The connector comprises an insulative housing, a plurality of terminals, an upper shell, a lower shell, and a casing portion. The insulative housing has a projection portion and a plurality of passageways defined in the projection portion. A USB cable is used to electrically connect a computer and other apparatuses. For example, input devices such as a mouse and a keyboard are connected through the USB cable to the computer. A USB connector is disposed at an end of the USB cable. The USB connector is inserted into a mount port disposed on a computer. When the USB connector is inserted into the mount port, a fastening claw in the USB connector is fastened to a fasten protrusion formed in the mount port, then the USB connector is fastened to the computer.
A USB connector replaces different kinds of serial and parallel port connectors with a standardized plug and port connection. For the successful utilization of a USB connector, the CPU must have an operating system that is USB compliant and that understands it. This permits hot swapping to be done without the need to shut down and reboot the system each time a peripheral device is attached or removed from the CPU. A USB bus transfers signals and power over a cable having four wires. The signaling occurs over two wires in point-to-point segments. The maximum length of a cable segment is five meters. A USB bus connects USB devices with a USB host. There is only one USB host on any USB system. A USB host has a power management system which is independent from that of the USB. The host acts as master of the bus, acknowledging attachment and removal of peripherals, initiating enumeration processes and all subsequent USB transactions on the bus, collecting status and activity statistics, and controlling electrical interface between the host and USB peripherals. The USB system software interacts with the host's power management system to handle system power events. USB supports functional data and control exchange between the USB host and a USB device in either a unidirectional fashion or a bidirectional fashion. Data transfers take place between host software and a particular endpoint on a USB device. Hubs provide additional attachment points to the USB. The host queries the hub to determine the reason for the notification. The hub then responds by identifying the port used to attach the USB device. The USB hub uses a standardized connector at the downstream ports to provide universal connectivity between peripheral devices and the computer. The USB standard defines two channels: a fast channel running at 500 mega-bits/second which will be used for monitors, networks, and printers; and a slow channel running at 100 kilo-bits/second which will be used for keyboards, the mice, scanners and modems.
The USB connector is getting more and more common for connection ports in personal computers because the connection between personal computer and external peripheral equipments can be simplified. Almost every computer is equipped with two or more USB female sockets. The peripheral apparatus of the computer is mainly equipped with the USB male plug. The USB connector can unify various specifications for various connectors so as to overcome the conventional shortcoming of providing a specific connector for a specific apparatus. A universal serial bus (USB) connector provides a standard and inexpensive way to connect a peripheral device with a computer host. Thus, without USB, a personal computer requires separate interfaces for its keyboard, monitor, modem, printer, microphone, joy stick, mouse, scanner, and so forth. With USB, USB-capable peripherals can be connected directly to USB hubs on the bus, without the need for any specialized software interfaces or mechanical or electrical interfaces. USB connectors provide an integrated connector function for various peripherals which not only provides for transmission speed, construction, and maintenance that is more convenient than conventional single-application connectors. The capabilities of a computer, e.g. a personal computer, laptop computer, hand-held computer, work station, server or the like, are maximized by utilizing a variety of external peripheral devices that are connected to the computer. One USB port can be used to connect over 100 peripheral devices.