USB stands for ‘Universal Serial Bus’, a data transfer system developed in the 1990s as an industry standard for transferring data between PCs and other peripheral devices.
To accommodate the different peripheral devices available (for example, mice, keyboards, mp3 players), a number of USB types have been released over the years (USB A, USB B, USB mini, USB micro etc.). The search for improvements in data transfer speed has also made it necessary for new versions (USB 1.1, USB 2.0 etc.) to be released.
This has left the USB landscape littered with an excess of USB types and versions, many of different size and shape to those that came before.
The following page lays out the different USB plugs you are likely to see available for today’s PCs and laptops.
USB ‘type’ refers to the basic shape of the plug (and socket). Originally, USB offered only two types, USB A and USB B. Since then a third type has been added: USB C, as well as the mini and micro versions, which will be covered later. However, Types A and B are still the ones used most commonly.
USB Type A
This flat rectangular shape is what most people think of as a ‘USB’. You will find ports that fit this classic type on almost all computers sold today. Despite the launch of different versions of the Type A plug, the shape has not changed. This means that any version of the USB Type A plug is compatible with any version of the USB Type A port found on a computer.
USB Type B
The squarer-shaped USB Type B is used for larger peripheral devices, such as printers and scanners. You will not find USB Type B ports on any computer, only on peripheral devices. The shape of Type B plugs has changed with each new USB version, though they remain square-looking.
USB Type C
The new type of USB plug was launched in 2014 (around the time USB 3.1 was developed) and only a limited number of computers have them. Its flat, rectangular design is symmetrical, meaning it can be plugged in with either flat side facing up. It can also be used for high-speed data transfers between two USB 3.1 devices. Some computers can charge through their USB C port, though it is recommended that you check the specifications before attempting this.
USB mini connectors were brought in to accommodate smaller devices such as smartphones and digital cameras. Mini A was developed to allow On-The-Go (OTG) devices that were usually peripheral, such as smartphones and tablets, to function as hosts. This meant that a range of devices — including keyboards and mice — could be attached and used with the OTG host device.
Primarily used for OTG devices, the mini A plug fell out of favour and has been superseded by micro plugs.
You may recognise this as the plug used to charge some of the first smartphones available.
Micro connectors will be familiar to most people as the charger for all modern Android smartphones. The universal popularity of the micro B plug meant that micro A was quickly discontinued on most devices.
Used for the next iteration of OTG devices, the micro A does not have its own dedicated port but rather fits into a special AB port, which accommodates both micro A and micro B.
The micro B plug gained much popularity when almost all the different Android manufacturers opted to use the micro B as their standard charging plug and port.
Over the years, the designers of USB have made some changes. These include increasing data transfer speeds and improving USB’s charging capabilities.
In some instances, a new design of USB would accompany a new version. Some of these were ‘backwards compatible’ — made so the new design could work with the old design.
Although there are earlier versions, USB 1.1, released in 1998, was the first iteration to be widely used among the public. This offered a data transfer rate of up to 12Mbit/s (Full Speed). No mini plugs were available for this or any version before 1.1.
With the launch of USB 2.0 came the first mini plugs: mini A and mini B. USB 2.0 also offered data transfer speeds of up to 480 Mbit/s (High Speed) and a charging current of 500 mA.
A fact of USB ports is that they can function in either a low-power state or a high-power state. When a device is attached, the default state is low power. However, if both host and device are compatible, they can enter a high power state, at which point the device is able to draw more power.
The development of 3.0 brought with it a new SuperSpeed top transfer rate of 5.0 Gbit/s and increased current of 150 mA and 900 mA for low-power and high-power devices respectively. With USB 3.1 came the new SuperSpeed+ with increased transfer rates of 10 Gbit/s, while USB 3.2 pushed speeds to 20 Gbit/s. However, not all micro USB 3.0 plugs are backwards compatible with older USB versions; when they are compatible, faster speeds are not guaranteed.
At CMD, we supply USB 2.0 as standard, with USB 3.0 available upon request. For more information, ring (0)1709 385485 or contact us here.
Colours and SuperSpeed
To identify cables and ports that feature the SuperSpeed transfer rates found with USB 3.0/3.1/3.2, manufacturers were encouraged to produce plugs and ports in a blue colour and carrying a ‘SS’ logo.
In many cases, SuperSpeed cables are entirely blue, with plugs and ports having a blue interior.
This distinguishes them from earlier USB versions, which were colour-coded either black or white.
USB 3.0 micro B cables (for use with mobile phones, tablets and external hard drives) can be identified by the new shape of the connectors: the micro B 3.0 connectors are wider than those on the 2.0 version and appear to have two sections.
This new shape means that although micro B 2.0 plugs will work in the new micro B 3.0 ports, the reverse is not the case.
Read the following posts for more information about USB charging and data transfer:
USB data transfer guide