A P P E N D I X
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USB 2.0 specification primer
USB connectors and cables
USB connectors
There are two types of full-size USB connectors: Series-A and Series-B, also known as Type-A and
Type-B, respectively. Either connector type can be a receptacle or a plug.
Series-A receptacles are used as outputs from host systems and hubs.
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Series-B receptacles are used as inputs to hubs or devices.
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Series-A plugs are always oriented toward the host system and connect to Series-A
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receptacles.
Series-B plugs are always oriented toward a USB hub or device and connect to Series-B
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receptacles.
N O T E
Smaller versions of the Series-A and Series-B connectors, called mini-A and mini-B, and micro-A
and micro-B, are available and conform to the same rules as full-size USB connectors.
T I P
Although USB 2.0 specifications require that USB connectors can be "hot plugged" (for example,
you can insert a USB connector with power on without damage to the circuitry), we recommend
that you connect all your devices and cables before you turn on the power. If you connect a device
when the power is already on, and the system doesn't work correctly, disconnect the power from all
active devices in the USB circuit, and then connect the power again.
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