USB, or Universal Serial Bus, is a standard connection type and communication medium between a wide range of electrical devices, including computers and peripherals.
It was introduced in 1996. The idea was to standardize communication or data transfer between peripheral devices and computers by replacing older communication interfaces, such as parallel and serial ports (don’t confuse them with communication/data transmission process) and FireWire.
Do you know? The USB standard is regulated by the USB Implementers Forum (USB-IF), established by founding companies, including IBM, Intel, Microsoft, and Nortel.
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Where is USB Used?
As an industry-standard, USB cables are used to connect desktops or laptops to external hardware devices such as keyboards, mice, flash drives, printers, and gaming controllers.
The USB interface has become widely popular in recent years, so much so that you can easily find them even in vehicles and electrical outlets in homes. Modern smartphones, tablet computers, and many portable devices now support USB cables and connectors for fast charging over other cable types.
Advantages of USB Interface
While USB was primarily developed to normalize connectivity between personal computers and auxiliary devices, there are several other USB interface advantages.
- It is self-configuring, meaning there is no need to adjust/configure its settings before use.
- USB devices can be added or replaced to a system without shutting or rebooting the system (hot-swappable).
- Its electric power supply capability allows small devices to be powered without an additional power supply cable.
- The USB data transfer protocol and signaling are more reliable irrespective of their version.
Types of USB Based On Their Version
There are two ways a USB cable can be classified; based on its version or generation, which concerns the functionality (data transfer rate) of the cable, and by its physical design.
Before we get started with the different types of USB cables, let’s first understand a few terms associated with them. A typical USB cable has two connectors, one on each side. One is for the host, which includes all types of computers (PCs, tablets), and the other is for the receptor, any portable device (smartphones) that you need to transfer data to. The slot where a USB is inserted is called a Port or the receptacle. Anyhow, let’s get to the matter in hand.
Since 1996, four major versions or generations of USB standards have been introduced. These are USB 1.0, USB 2.0, USB 3.0, and USB4. The USB4 being the most recent one.
| USB Version | USB 1.0 and USB 1.1 | USB 2.0 | USB 3.0 | USB 3.1 (Gen 2) | USB 3.2 |
| Data Transfer Rate | 1.5 Mbps (Low Speed) 12 Mbps (Full Speed) |
480 Mbps (High Speed) |
5 Gbps (SuperSpeed) |
10 Gbps (SS+) |
10 and 20 Gbps (SuperSpeed+) Over USB-C cables |
A table showing different versions of USB and their supporting transfer speeds: Note USB4 is excluded
USB 1.0 and USB 2.0
The original USB, USB 1.0, supports a dual-speed bus with data transfer rates of 1.5 Mbit/s for inexpensive, low data rate devices (keyboards, mice) and 12 Mbit/s for high data rate devices (printers, disk drives). This multi-bus architecture is extended to USB 2.0 (launched in 2001). However, it added a third, ‘high-speed’ bus with a maximum data transfer rate of 480 Mbit/s.
The Universal Serial Bus first came to the spotlight in 1988 (when USB 1.1 was introduced) with the Apple iMac release. It was the first widely recognized product to feature USB technology. Soon, PC manufacturers followed suit by replacing legacy ports with USBs on their products. Thus, the USB’s initial success is tied with that of iMac’s.
USB 3.0
The USB 3.0, released on 12 November 2008, was a game-changer in the industry. It introduced a much higher speed bus with a data transfer rate of up to 5 Gbit/s (in addition to existing transfer speed modes) and higher power output (900mA compared to 500mA in previous versions). Moreover, it was made backward compatible with USB 2.0, allowing interoperability. This version of USB is popularized as SuperSpeed.
USB 3.0 Gen 1 ports | Image Courtesy: Wikimedia Commons
The USB 3.0 standard was replaced by USB 3.1 in 2014. The data transfer rate in USB 3.1 Gen 2 (SuperSpeed+) was increased to 10 Gbit/s. One of the important changes put forward by the USB 3.1 was replacing their previous 8b/10b encoding scheme with a more efficient 128b/132b, a variant of 64b/66b encoding (that converts 64-bit data to 66-bit line code). It significantly reduces encoding overhead, resulting in comparatively higher effective data-transfer rates.
The following USB 3.2 standard was released in 2017. As expected, it introduced a new, much faster transfer mode while retaining all existing modes. It enabled USB-C (3.1 supported) cables to operate at 2X their initial speed (5 Gbit/s to 10 Gbit/s for USB-C 3.1 Gen 1 cables, and 10 Gbit/s to 20 Gbit/s for Gen 2 cables). We will talk about USB-C cables later on.
USB4 or USB 4.0
The latest USB standard, USB4 (or USB 4), extends the existing capabilities of USB-C cables by enabling the highest USB bandwidth available. It is based on the Thunderbolt protocol that offers advanced features such as bi-directional data transfer (send and receive data from both ends), Dual protocol data, and video transfer over a single cable with low latency.
USB4 is compatible with Thunderbolt 3 and backward-compatible with USB 2.0 and USB 3.2 specifications. It supports maximum data transfer speeds of 40 Gbit/s. In existing USB-C cables, those speeds are achieved by two-lane operation, in which two of the lanes in a cable transfer data simultaneously.
Intel’s 11th generation core processor ‘Tiger Lake’ is the first product to support USB4 or Thunderbolt 4 standard.
Types of USB Cables [Based On Their Physical Structure]
From smartphones and small portable devices to computers of all kinds, almost every electronic product now comes with USB ports or has USB support. However, the physical specifications of USB ports and connectors differ from one product class to another.
Based on the physical attribute or layout, USB cables can be classified into three types: USB-A, USB-B, and USB-C.
USB Type-A
The USB-A is perhaps the most popular USB (connector or port) that you can found on your PCs, gaming consoles, portable media players, and smartphone charging ports. A standard USB Type-A plug is flat and rectangular in shape.
The older USB Type-A connectors and ports that support USB 2.0 standard have four internal pins; one pair is for carrying data, and the other is for power. With the USB 3.0 standard introduction, five extra pins were added to the original design to make the new USB Type-A (SuperSpeed) ports and connectors faster and backward compatible with older USB versions.
USB Type B
The USB Type B ports are usually found on receptors or peripheral devices such as printers and scanners that operate on high data rates and are relatively larger in size (compared to other peripheral devices).
In most cases, the USB cable that connects a computer with a printer or scanner has a USB Type-B connector on one side and a Type-A connector on the other. While they are usually dual-purpose, some Type-B ports only allow power transmission from the host.
Two versions of USB Type-B exist. The original USB Type-B connector has a square cross-section with a slightly oblique top exterior bezel. It supports data transfer speeds up to 480 Mbit/s (USB 2.0).
USB 3.0 Type-B connector | Image Courtesy: Anıl Öztaş
An improved version of the Type-B connector, Type-B SuperSpeed, was introduced to make them USB 3.0 standard compliant. With a data transfer speed of more than 5 Gbit/s, the Type-B SuperSpeed cables are ideal for connecting PCs with external hard drives and audio interfaces.
USB Mini and Micro Type B
USB Micro-B connector
Mini-USB connectors were first introduced in 1998 for electronic devices such as early smartphones and tablet computers. While Mini-A connectors have been long discontinued, Mini Type-B is still supported by a small number of devices.
Micro-USB connectors are developed explicitly for modern portable devices, such as smartphones and cameras, which are much thinner than early devices. The thickness of a Micro-USB connector is almost half that of Mini-USBs.
USB-C
USB-C is an industry-standard for high-speed data and power transfer that are now found on an increasing number of devices, including the newest smartphones, external SSDs, and expensive laptops.
A USB-C connector, at first, may appear similar to a Micro-USB connector since both have curved edges, though a USB-C connector is slightly thicker and wider.
USB-C connector | Image Courtesy: Wikimedia Commons
Perhaps the most critical and rather desirable feature of USB-C connectors is flippability. It means that USB-C connectors have no up or down orientation (as the case with USB-A and USB-B connectors). You can insert them correctly every time without flipping.
Another advantage of USB-C cables is they carry a minimum of 3 A current at 60 W. The USB-C to USB-C cables are designed to carry a higher 5 V current.
The USB-C cables based on USB 3.1 standard have a maximum data transfer limit of 10 Gbit/s. Older cables that support USB 2.0 can carry only up to 480 Mbit/s.
USB On-The-Go
USB OTG setup | Wikimedia Commons
The USB On-The-Go, or OTG, is a USB specification that allows certain devices to perform both host and receptor roles. For example, with OTG, a smartphone may read data as a host when connected to a digital camera or a flash drive but act as a receptor when connected to a host PC.
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What Is In The Future?
There is a popular saying that ‘nothing lasts forever,’ and it could not be more precise in the world of technology. However, there are instances where you can predict whether something as disruptive as USB-C will out-stay all or not. Although Type-A and Type-B ports and cables remain widely in use, USB-C is primed to replace them in the near future.
USB-C port on MacBook | Image Courtesy: Maurizio Pesce/Flickr
The most recent USB-C ports support the Thunderbolt 3 protocol that allows maximum data transfer speeds of up to 40 Gbit/s. The USB4, which is yet to make it to the mainstream market, will standardize Thunderbolt 3 speeds.
High throughput of data and power enables USB-C connectors to connect directly with several audio and video interfaces without the need for any adapters. They include MHL (Mobile High-Definition Link), HDMI, and DisplayPort devices.
Since 2014, an increasing number of electronic devices, including smartphones, PCs/laptop motherboards, and external hard-drives, have become USB-C enabled. The double-sided USB-C cables that plug into both host and receptor are faster and more efficient than older Type-A and Type-B connectors.
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The growing ecosystem of USB-C means you’ll soon require supported ports and connectors to transfer data and charge your laptops. Though Apple was the first company to introduce USB-C ports on its devices, they are increasingly found on other mainstream devices. Expensive PCs and laptops have at least one USB-C port.
