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PC Hardware in a Nutshell, 3rd Edition by Barbara Fritchman Thompson, Robert Bruce Thompson

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USB Cables and Connectors

USB connectors and cables are simple and rigidly standardized. USB defines three plug/jack combinations, designated Series A, Series B, and Series mini-B.

Tip

Series mini-B connectors are smaller versions of the standard Series B connector, designed for devices such as digital cameras, for which a standard Series B connector is physically too large. Most devices that use Series mini-B connectors come with a Series-A to-Series-mini-B cable.

The narrow Series A jacks, shown in Figure 24-2, appear on the back of a PC or USB hub, and may be labeled “down” jacks. These provide connection points for USB peripherals, including USB hubs. Some USB peripherals have permanently connected cables that terminate in a Series A plug. Series A plugs always face upstream, toward the host system, and Series A jacks always face downstream, toward the device.

USB Series A connector

Figure 24-2. USB Series A connector

Peripherals that do not have a permanent cable instead have a Series B jack, shown in Figure 24-3. Series B plugs always face downstream, and Series B jacks always face upstream. Use a standard USB A-B device cable to connect these peripherals to the PC or hub.

USB Series B connector

Figure 24-3. USB Series B connector

A USB cable uses four wires, two each for data and power. The data wires are a green/white twisted ...

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