英语翻译USB supports following data rates:• A Low Speed rate of 1.5 Mbit/s (187.5 kB/s) is defined by USB 1.0.It is very similar to full speed operation except each bit takes 8 times as long to transmit.It is intended primarily to save cost

英语翻译USB supports following data rates:• A Low Speed rate of 1.5 Mbit/s (187.5 kB/s) is defined by USB 1.0.It is very similar to full speed operation except each bit takes 8 times as long to transmit.It is intended primarily to save cost
英语翻译
USB supports following data rates:
• A Low Speed rate of 1.5 Mbit/s (187.5 kB/s) is defined by USB 1.0.It is very similar to full speed operation except each bit takes 8 times as long to transmit.It is intended primarily to save cost in low-bandwidth Human Interface Devices (HID) such as keyboards,mice,and joysticks.
• The Full Speed rate of 12 Mbit/s (1.5 MB/s) is the basic USB data rate defined by USB 1.1.All USB hubs support Full Speed.
• A High-Speed (USB 2.0) rate of 480 Mbit/s (60 MB/s) was introduced in 2001.All high-speed devices are capable of falling back to full-speed operation if necessary.
Experimental data rate:
• A SuperSpeed (USB 3.0) rate of 5.0 Gbit/s (625 MB/s).The USB 3.0 specification was released by Intel and its partners in August 2008,according to early reports from CNET news.Products using the 3.0 specification are expected to arrive in 2009 or 2010.[7]
USB signals are transmitted on a twisted pair data cable with 90Ω ±15% impedance,[8] labeled D+ and D−.These collectively use half-duplex differential signaling to combat the effects of electromagnetic noise on longer lines.Transmitted signal levels are 0.0–0.3 volts for low and 2.8–3.6 volts for high in Full Speed (FS) and Low Speed (LS) modes,and -10–10 mV for low and 360–440 mV for high in High Speed (HS) mode.In FS mode the cable wires are not terminated,but the HS mode has termination of 45Ω to ground,or 90Ω differential to match the data cable impedance.
A USB connection is always between a host or hub at the "A" connector end,and a device or hub's upstream port at the other end.The host includes 15 kΩ pull-down resistors on each data line.When no device is connected,this pulls both data lines low into the so-called "single-ended zero" state (SE0 in the USB documentation),and indicates a reset or disconnected connection.
A USB device pulls one of the data lines high with a 1.5 kΩ resistor.This overpowers one of the pull-down resistors in the host and leaves the data lines in an idle state called "J".The choice of data line indicates a device's speed support; full-speed devices pull D+ high,while low-speed devices pull D− high.

英语翻译USB supports following data rates:• A Low Speed rate of 1.5 Mbit/s (187.5 kB/s) is defined by USB 1.0.It is very similar to full speed operation except each bit takes 8 times as long to transmit.It is intended primarily to save cost
USB接口支持以下数据传输率：
•低速增长率为1.5兆位/秒（ 187.5字节/秒）的定义是通过USB 1.0 .这是非常类似的全速运行,除非每比特需要8倍,只要转交.它主要是为了节省成本在低带宽的人机接口设备（的HID ） ,如键盘,鼠标,和操纵杆.
•在全速率12兆位/秒（ 1.5 MB /秒） ,这是基本的USB数据传输速率的USB 1.1所定义.所有USB集线器支持全速.
•一种高速（支持USB2.0 ）率为480兆位/秒（ 60 MB /秒） 2001年推出.所有高速器件能够回落至全速运行如果有必要.
实验数据速率：
•一个超（ USB接口3.0 ）率为5.0 Gbit / s的（ 625 MB /秒） .的USB 3.0规范是由英特尔公司和其合作伙伴在2008年8月,据初步报告从CNET新闻.产品使用3.0规范,预计将在2009年或2010年.[ 7 ]
USB信号传输的双绞线电缆的数据90Ω ± 15 ％阻抗,[ 8 ]标记d +可与D - .这些集体使用半双工差分信号打击的影响,电磁噪声更长线.发送信号水平0.0-0.3伏特低电压和高2月8号至三月六号在全速（财政司司长）和低速（镑）的模式,-10-10 mV的低和高360-440毫伏高速（高速）模式.在财政司司长模式电线电缆没有终止,但高速模式已经终止45Ω至地面,或90Ω差分相匹配的数据电缆阻抗.
USB连接总是之间的主机或集线器上的“ A ”连接器结束,设备或集线器的上行端口的另一端.主机包括15 kΩ下拉电阻对每个数据线.当没有设备连接,这两个数据线拉低到所谓的“单端零”状态（ SE0在USB文件） ,并显示出重置或断开连接.
USB装置拉一个数据线高1.5 kΩ电阻.这overpowers一个下拉式电阻器的主机和叶片的数据线在空闲状态被称为“ J ”的.选择数据线显示设备的速度支持;全速设备拉d +可高,而低速设备拉名D -高.