USB 机械特性

提供了电缆、连接器及连接不同USB设备的电缆部件机械和电气方面的规范，包括尺寸、材料、电气及可靠性等方面的要求。同时说明了外部USB设备互连的最低要求，只要符合这些最低要求，也可以使用别的材料。USB电缆由2条电导线和2条信号线组成。USB可以在2种数据速率下工作；全速为12Mbit/s，要求使用带2条电导线和双绞信号线的具有屏蔽层的电缆；低速为1．5Mbit/s，降低了对电缆的要求，不需要使用蔽层和双绞信号线，连接器设计为热插拨，在USB插头的图标上提供了标识以便于正确定向。

USB Mechanical Specification

The mechanical and electrical specifications for the cables, connectors, and cable assemblies used to interconnect USB devices are provided,including dimensions,materials,electrical and reliability requirements. The minimum requirements for the external USB interconnection are explained.Substitutes may be used as long as the minimum requirements are met. USB cable consists of four conductors, two power conductors and two signal conductors. USB can operate at two speeds.Full speed, 12 Mbit/s, needs shielded cable with two power conductors and twisted pair signal conductors. Low speed, 1.5 Mbit/s,relaxes the cable requirement, shielding and twisted pair signal conductors are not necessary.The connectors are designed exchangeable when powered. The USB icon on the plug provides identifier for proper orientation.