Nepedia
Back to Discover
Advanced Reader
💻

USB

technology Maturity 7-9 Next article →

The Universal Serial Bus, or USB, is an industry standard for digital data transmission and power delivery.

USB Icon
USB Icon

It provides a way for many types of electronics to communicate with one another. This standard defines the physical interfaces, which are the actual plugs and ports, and the communication protocols used for data. A host, such as a personal computer, manages the connection to peripheral devices. These peripherals include keyboards, mice, displays, and mass storage devices. USB can also connect to intermediate hubs. These hubs multiply the number of ports available to a single host.

USB-C connector and receptacle
USB-C connector and receptacle

USB operates through a specific architecture involving hosts and peripherals. The host acts as the master controller in a tree network topology. Peripheral devices act as slaves that follow the host's instructions. This system is self-configuring, meaning the user does not need to adjust settings for speed or data formats. It is also hot-swappable, so devices can be exchanged without shutting down the host computer. USB can also supply electric power directly to small devices. This removes the need for extra power supply cables for many accessories. However, the architecture has limits. A host cannot broadcast signals to all peripherals at once. Each device must be addressed individually by the host.

There are several different types of USB connector interfaces. The legacy Type-A and Type-B connectors are very common. Type-A connectors are typically found on hosts, while Type-B connectors are found on peripheral devices. These came in Standard, Mini, and Micro sizes. The Standard size was largest and used for desktop equipment. Mini-USB was made for mobile devices, but it was quickly replaced by the thinner Micro-USB.

USB Type-A receptacle Black
USB Type-A receptacle Black

The modern Type-C connector, or USB-C, is the current standard. It is required for USB4 and is reversible, so it can be plugged in either way. USB-C can replace many other connectors by supporting power, displays, and data all at once.

USB Type-C Receptacle Pinout
USB Type-C Receptacle Pinout

USB has evolved through four main generations of specifications. These include USB 1.x, USB 2.0, USB 3.x, and USB4. The early versions, such as USB 1.0 and 1.1, offered signaling rates of 1.5 to 12 Mbit/s in half-duplex mode. USB 2.0 was released in 2000 and provided 480 Mbit/s.

USB 5Gbps logo
USB 5Gbps logo

USB 3.0 arrived in 2008 and introduced the SuperSpeed architecture. This version used a new signal coding scheme called 8b/10b symbols to reach 5 Gbit/s. It required five additional wires, bringing the total to nine wires. USB 3.1 later added the SuperSpeedPlus protocol, which uses 128b/132b symbols to reach 10 Gbit/s.

USB 10Gbps logo
USB 10Gbps logo

USB 3.2 added a second lane to allow for even higher speeds.

USB4 represents the latest major leap in technology. It was introduced in 2019 and uses a connection-oriented tunneling architecture. This allows it to combine multiple protocols onto a single physical interface.

USB 40Gbps logo 01
USB 40Gbps logo 01

USB4 can tunnel Thunderbolt 3 protocols, specifically PCI Express and DisplayPort. This means a single USB4 cable can carry high-speed data and video signals simultaneously. The speed of USB4 is much higher than previous versions. USB4 2.0 can reach signaling rates of up to 80 Gbit/s in full-duplex mode.

USB 80Gbps logo
USB 80Gbps logo

This represents a massive increase from the original 1996 specifications.

Before USB became the standard, computers used many different, specialized ports. These included serial ports, parallel ports, and game ports. There was also the Apple Desktop Bus, or ADB. The USB Implementers Forum developed USB to replace these various interfaces with one single standard. This was first introduced in 1996. By standardizing the connection, it became much easier for manufacturers to build devices. They no longer had to develop proprietary interfaces for every new product. This helped USB become commonplace on everything from smartphones to game consoles.

USB is significant because it manages both data and high levels of power. The USB Power Delivery, or USB-PD, standard was updated in 2021. The latest versions can provide up to 240 watts of power for charging batteries and running devices.

Certified USB
Certified USB

This high power capacity allows USB-C to replace many different types of power supplies. Because USB is backward-compatible, newer versions can still work with older devices. This usually means the newer device will just run at the slower speed of the older standard. This compatibility ensures that the digital world stays connected even as technology changes rapidly.

735 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (37)
USB-C connector and receptacle.webp
File:USB 80Gbps logo.svg
USB 80Gbps logo.svg
File:Certified USB.svg
Certified USB.svg
File:Certified Hi-Speed USB.svg
Certified Hi-Speed USB.svg
File:USB 5Gbps logo.svg
USB 5Gbps logo.svg
File:USB 10Gbps logo.svg
USB 10Gbps logo.svg
File:USB 20Gbps logo.svg
USB 20Gbps logo.svg
File:USB 40Gbps logo 01.svg
USB 40Gbps logo 01.svg
File:USB SuperSpeed 5 Gbps Trident Logo.svg
USB SuperSpeed 5 Gbps Trident Logo.svg
File:USB SuperSpeed 10 Gbps Trident Logo.svg
USB SuperSpeed 10 Gbps Trident Logo.svg
File:USB SuperSpeed 20 Gbps Trident Logo.svg
USB SuperSpeed 20 Gbps Trident Logo.svg
File:USB Type-A receptacle White.svg
USB Type-A receptacle White.svg

+ 25 more

More to explore

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.