When it comes to USB, everyone must be both familiar and unfamiliar. Familiar is because we use it every day, while unfamiliar is because its complex classification makes it difficult for many people to distinguish. So, how to accurately identify USB?

In fact, understanding USB interfaces mainly comes from two aspects: transmission standards and interface standards. Transmission standards mainly refer to transmission rates, while interface standards correspond to their interface appearance.

The USB (Universal Serial Bus) bus protocol is a serial interface standard developed by seven companies including Intel, Compaq, Microsoft, IBM, DEC, Northern Telecom, and NEC in Japan. There are mainly four types:

1. The Birth of USB - USB 1.0

The USB 1.0 specification was officially proposed in 1996, but the bandwidth was only 12Mbps, about 1.5MB/s, which was very slow. Moreover, at that time, there were very few peripheral devices that supported USB, so it was not taken seriously. The maximum output current was 5V/500mA.

2. A qualitative leap - USB 2.0

USB devices have gained widespread popularity due to their portability, standardized features, and support for hot swapping. In 2000, the new USB 2.0 specification was introduced, which achieved a speed of 480Mbps, approximately 60MB/s, and is backward compatible with the 1.1 specification, with a maximum output current of 5V/500mA.

3. Strong Breakthrough - USB 3.0

Greatly improve the theoretical speed of transmission bandwidth to 5Gbps, provide better power management, support standby, sleep, pause and other states, identify devices faster, and increase the maximum output current to 5V/900mA.

4. Quick Reminder - USB 3.1

USB 3.1 pursues faster speed, with a theoretical speed of 10Gbps, twice that of USB 3.0, and a maximum output current of 20V/5A.