Communication in the age of computers and smartphones would be practically unthinkable without USB connectors. Nowadays, the serial interface is works for any kind of data transfer between two devices that you can connect to each other during operation. In this article, we explain how the individual USB connector types differ from each other and what they are using for.
However, not all USB ports are the same: once introduced as a standard interface, it has evolved into numerous plug and socket forms. Lets find out detailed overview and the differences.
- USB is based on a serial architecture. Data can thus be transferred bit by bit (i.e., in series) from one device to another.
- If you use a USB hub, a maximum of 127 peripherals may be connected to the master via one port at the same time. In addition, there should be at least a 5-meter distance between two ports or hubs.
- USB-C is the only standard that is compatible with all other USB specifications.
The history of the USB standard
The USB standard (“Universal Serial Bus“) was introduced in 1996 by well-known manufacturers such as Intel to replace the then prevailing serial, parallel, and COM interfaces. The aim was to create a universal connection with computers, and it could interconnect peripherals in the simplest possible way.
Thanks to the “hot plugging” option, USB is even use in smartphones and televisions. Also, modern household appliances such as coffee machines or refrigerators have long been equipped with it.
USB 1.0 and USB 1.1 – The first generation
The launch of USB 1.0 at the end of 1996 was not under a good star: Although the transfer rate of 12 Mbit/s was significantly higher than that of the common interfaces, the common Windows operating systems (mostly Windows 95 and Windows NT) did not support the standard.
In addition, there was a lack of suitable peripheral devices, which is why USB was far behind Apple’s Firewire bus (IEEE1394), which also had a data rate that was more than 30 times higher.
In 1998, a revised version was released with USB 1.1, eliminating some errors in the internal software. However, since it did not adjust the data rate, the new specification did not bring the hoped-for success.
USB 2.0 – The most widely used generation
The big breakthrough came in 2001 with the introduction of USB 2.0. With a leap from 12 Mbit/s to 480 Mbit/s, the transfer speed was suddenly increased by a factor of 40.
In addition, the maximum current was raised from 0.1 A to 0.5 A. This means it can connect any device with a higher energy requirement. Such as external hard drives, cameras, or video recorders, without any problems.
Current peripheral devices such as keyboards and mice work with the USB 2.0 standard.
USB 3.0 and USB 3.1 – The latest generation
In 2008, USB 3.0 was the next step on the evolutionary ladder. With 5 Gbit/s, a decent shovel has been added to the previous data rate. In addition, USB 3.0 connectors have five additional contacts for sending and receiving (SSRX+ and SSRX- as well as the ground line GND) and a maximum current of 0.9 A compared to the 2.0 versions.
Two new standards emerged from USB 3.0. standard: USB 3.1 (Gen1) is a technically improved USB 3.0 with a similar transfer rate and the same specifications, whereas USB 3.2 (Gen2) SuperSpeed+ would theoretically even be 10 Gbit/s possible. And the amperage has also increase: with a maximum of 5A, there are no longer limitations with the connected devices.
USB 3.2 – The coming generation
The latest USB standard, 3.2, was released in July 2017 and is still in the technical implementation phase. However, initial tests have already been very promising, and data rates of up to 20 Gbit/s should even be possible with the new specifications.
The following overview shows a direct comparison of the USB standards mentioned above:
|Max transfer rate||12 Mbps||480Mbps||5 Gbps||10 Gbps||20 Gbps|
|Maximum current||0.5A||0.5A||0.9A||5A||Not specified|
Enjoying this guide on USB connector types? You might also interested to read in How to set up WLAN repeater.
Different USB connector types
Over the years, in addition to the various standards, a whole range of USB plug and socket types have been established, designed for different application areas.
USB Type A
USB Type A is the most common USB connector type used on mice, keyboards, USB sticks, or playback devices. By default, the rear and side USB ports on computers or notebooks are also type A.
USB type B
This type of connector is rarely found nowadays. Only some older printers or fax machines still have a USB type B connector. However, only very few modern computers have the appropriate mating connectors, so a Type-B to Type-A cable is usually used in such cases.
USB Mini B
The Mini USB Type B is a shrunken version of a conventional USB connector with smaller dimensions, which is mainly not found in MP3 players or digital cameras.
USB Micro A and Micro B
USB Micro A and Micro B (only type B is shown in the picture) differ mainly by their shape: A Micro A connector is built rectangular; Micro B connectors end trapezoidal. Micro USB Type A is rarely found on some external hard drives or other small peripherals.
On the other hand, Type B is the common standard on current smartphones. Micro USB connections can work in both directions, so data transfer is possible while the phone is charging, for example.
USB 3.0 Micro B
This USB connector type is mainly found on mobile devices (e.g., external hard drives or card readers) with USB 3.0. Visually, the USB 3.0 Micro B resembles an extended USB Micro connector, which is basically what it is.
USB Type C
USB Type C is compatible with all USB specifications and will eventually replace the previous USB-A and USB-B ports. What’s special about this connector is that you can plug it in any direction. USB C is currently the standard for all USB 3.1 applications. This USB connector type is currently mainly found in new smartphones, and it is also used to display connections.
What about the colors on USB connector types?
As if the different types weren’t confusing enough, USB plugs have not only different shapes but also different colors in relation to the ports:
- Black/white indicates a USB 1.0 or USB 2.0 standard connector.
- Blue stands for a new USB 3.0 port with a particularly fast transfer rate.
- Yellow stands for ports with a permanent power supply (even when the computer switch is off).
You can also read these articles: