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我知道目前市面上有很多你说的那种延长线，我就是想知道那些延长线是否符合标准规定。嘿嘿，不要说我抬杠哟。<br /><br /><br />下面是USB 2.0协议的一段：<br /><br />6.2 Keyed Connector Protocol<br />To minimize end user termination problems, USB uses a “keyed connector” protocol. The physical difference in the Series “A” and “B” connectors insures proper end user connectivity. The “A” connector is the principle means of connecting USB devices directly to a host or to the downstream port of a hub. All USB devices must have the standard Series “A” connector specified in this chapter. The “B” connector allows device vendors to provide a standard detachable cable. This facilitates end user cable replacement. Figure 6-1 illustrates the keyed connector protocol.<br /><br />The following list explains how the plugs and receptacles can be mated:<br />- Series “A” receptacle mates with a Series “A” plug. Electrically, Series “A” receptacles function as outputs from host systems and/or hubs.<br />- Series “A” plug mates with a Series “A” receptacle. The Series “A” plug always is oriented towards the host system.<br />- Series “B” receptacle mates with a Series “B” plug (male). Electrically, Series “B” receptacles function as inputs to hubs or devices.<br />- Series “B” plug mates with a Series “B” receptacle. The Series “B” plug is always oriented towards the USB hub or device.
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