In terms of USB, what do “downstream” and “upstream” mean?

Hubs or ports for the Universal Serial Bus, or USB, allow a computer user to connect computer peripherals such as a monitor to a computer. The use of “A” and “B” connectors in USB ports distinguishes connections. “A” connectors connect to the computer upstream, while “B” connections connect to distinct peripherals downstream.

A USB 2.0 hub, for example, is used by an HP flat panel monitor. The hub has four downstream ports for connecting peripherals to the computer and an upstream port for connecting the monitor to the computer. A monitor is always connected via an upstream port, while a USB device is always connected via a downstream port.

Individual classes are used to classify USB devices. Microphones and speakers, for example, are classified as audio devices, but chip cards and smart cards are classified as chip card interface devices. Modems and speakerphones are examples of communication USB peripherals, while keyboards, joysticks, and mice are examples of human interface USB peripherals. Any device with class-specific details in its interface is considered a composite class item.

Hard drives, CD read/write drives, flash memory readers, media players, and digital cameras go into the hub category, whereas hard drives, CD read/write drives, flash memory readers, media players, and digital cameras fall into the mass storage category. Webcams and digital camcorders are examples of video class USB devices.

Read more: What Is the Number of Vertices in a Hexagon?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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