What Is USB (Universal Serial Bus)? Meaning, Types, and Importance

Universal serial bus (USB) is defined as a standard that mentions the specifications used by cables, ports, and protocols that enable simple and universally accepted connectivity between a host and peripheral device. This article explains what USB is, the types of USB, and the importance of the technology.

What Is USB (Universal Serial Bus)?

USB, or universal serial bus, is a mechanism used to connect peripheral devices to computers. Before the advent of USB technology, a PC typically included one or two serial connections, a parallel port, keyboard and mouse connectors, and in some instances, a joystick port.

The USB standard was established in the mid-1990s by a number of American companies, notably IBM, Intel, and Microsoft Corporation, as a more straightforward way to connect computer peripherals. The port provided a standard method for connecting various devices and offered considerable speed advantages over other alternatives.

Initially, USB technology acceptance was sluggish:

• Computer manufacturers were extremely slow to include the ports on their systems before USB-capable peripherals were available.
• Peripheral device manufacturers were similarly unwilling to promote USB products before USB ports were ubiquitous on newer computers.
• When the tech was initially launched, operating systems had relatively modest supporting capabilities.

The 1998 introduction of the first model of Apple Inc.’s iMac was a major breakthrough. By creating a popular and well-received machine with only USB connections, Apple forced other manufacturers to embrace the standard. Since then, the majority of peripheral devices, including printers, scanners, and keyboards, have all used USB. Even the creation of new technologies (like portable memory sticks popularly called USB storage, which eventually replaced floppy discs) was spurred by the acceptance of this standard.

USB design is now standardized by the USB Implementers Forum (USB-IF), which is composed of organizations that support and promote USB. Not only does the USBIF endorse the USB, but it also maintains the standard and enforces the compliance program.

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How does USB (universal serial bus) work?

A computer’s ‘bus’ is a network of cables transporting data between internal components or a computer and its external devices. It is a metaphor for an electronic busbar, which distributes electricity across big, energy-hungry locations such as factories or data centers.

Before the introduction of USB, any peripheral device was connected to a computer through a port of its own construction. Over the years, as the number of peripheral devices rose, a new standardized method of exchanging data from the primary host and a variety of devices was required. This eventually led to the invention of USB.

When a peripheral device is connected to a host computer by USB, the host machine will automatically determine the kind of device and install a driver that lets it function.

USB transmits data between two devices in smaller, bite-sized quantities known as “packets. Each packet transmits a predetermined amount of bytes (a digital information unit). This might include details such as the source and destination of the material, and any anomalies that may have been discovered.

The working of a USB can be broken down as follows:

• Data transfer in bulk: This type of transmission is employed by printers or digital scanners for huge quantities of data. It is generally a low-priority transmission and is not time-sensitive. The operation may be delayed if the host machine has many USB devices attached.
• Small packets for critical device connections: This feature is used by peripheral systems like keyboards and mice to transmit tiny quantities of data. These transmissions are frequently utilized for occasional but significant requirements. The remote device generates requests and waits for the host to enquire about the precise data it would need. The requests will be reattempted if the first request for transaction fails. Here, the USB would also inform you of any modifications in the device’s status.
• Control packet transfers for USB management: This data transmission is used to set up and manage USB devices. The host submits a request to the device, followed by data transmission. Control transfer is also used for status checks. At any one moment, only one control request can be processed.
• Real-time, uninterrupted data transfer in the isochronous mode: Isochronous transfer is used for audio, video, and other real-time data. During the transmission, errors may occur, but the transmission will not be paused to resubmit the packets. However, such transfers often include instances in which the fidelity of the data is not crucial, such as the transmission of audio parts in a Voice over Internet Protocol (VoIP) call that the listener may not detect. It is better to exclude these components than to resend data, which might result in audio glitches.

As the number of devices increases, the host maintains a record of the total amount of bandwidth requested by all isochronous and interrupt devices. Together, they may take up to 90% of the available bandwidth, which is 480 megabits per second for standard USB or 4.8 gigabits per second with USB 3.0.

The host prevents access to any further isochronous or interrupt devices once 90% has been consumed. Control packets and bulk transfer packets use any remaining bandwidth (which is always 10% at a minimum). Beyond this threshold, you cannot have multiple USB connections transferring data simultaneously.

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How do USB cables work?

The USB port is a standard interface for connecting cables to PCs and consumer electronics devices. Users can connect a specially designed wire called the USB cable to this port. One end of the cable connects to the host and the other to the peripheral, and depending on the type of USB, the two ends may or may not be symmetrical. 

USB cables may transmit both power and information. To accomplish this, any USB cable has two types of wires. One set transports current, while the other transmits data signals.

There are four metal strips inside the conventional USB 2.0 connection. The two outermost strips are the power supply’s positive and negative terminals. The two center strips are designated for data transmission. With the latest USB 3.0 connection, the inclusion of additional data-carrying strips increases the data transmission rate. Four added signaling lines enable USB 3.0’s superior speed.

Key features of USB

Universal serial bus connections (enabled by USB ports and USB cables) support the following:

1. Hot swapping

Hot swapping is one of the major characteristics of the USB. This functionality enables the removal or replacement of a device without requiring a system restart or interruption.

The PC has to be rebooted when installing or uninstalling a device from an older port. Electrostatic discharge (ESD), an unintended electrical current capable of inflicting extensive damage to fragile electronic devices, was initially averted by rebooting. With USB, this is not necessary. Hot swapping is fault-ruggedized, meaning it can continue functioning despite hardware failure.

2. Direct current transfer

Another aspect of USB is the usage of direct current (DC). Several devices are connected to a DC current through a USB power connection but do not communicate data. Notable examples include USB speakers, small refrigerators, keyboard lamps, and even USB-based device chargers.

3. The use of multiple contact points

All USB connections feature at least four contacts used for power, ground, and two data wires (D + and D -). USB 3.0 connectors and above have five contacts. The USB connection is intended to transmit 5V at a maximum current of 500mA. The USB connection may be inserted in only one direction. It is feasible to force an incorrect connection. However, this could result in device damage.

4. Shielding and protection

The USB connection is insulated, providing a metal casing that is not part of the circuit. This characteristic is crucial for maintaining the signal’s integrity in an electrically “busy” environment. All USB cables are wrapped in plastic at the connection end to avoid damage to the cable and electrical connection.

10 Types of USB

USB can be classified based on four generations of development or the type of cable connections they use. Let us first look at the four versions of USB that have developed over the years.

1. The original USB

Before USBs, systems had serial and parallel ports, as previously explained. Many computer manufacturers, like Intel, Microsoft, and Apple, worked together to develop a universal device that connected multiple external sources to a PC without requiring a reboot. This was the first generation, as available in the 90s.

2. USB 2.0

In 2000, USB 2.0 achieved widespread dominance. The transfer speed was the most significant difference between version 2.0 and version 1.1. The USB 2.0 delivered data at a rate of 480 megabits per second, which is forty times quicker than the USB 1.1. In addition to its significantly enhanced speeds, USB 2.0 was configurable with any USB 1.1 port and vice versa.

3. USB 3.0, 3.1, and 3.2

USB 3.0 was the first device of its kind to transport high-definition video efficiently. It was also known as SuperSpeed USB and had transfer speeds of 5 gigabits per second or approximately 5,120 megabits per second. However, similar to USB 1.0, USB 3.0 could not catch on, and its successors found much more acceptance.
Macbooks and Chromebooks were among the first laptops to adopt the 2014-introduced USB 3.1. The maximum transmission rate of USB 3.1 was 10 gigabits per second. Exactly three years after this, USB 3.2 was launched with transmission rates of 20 gigabits per second, two times faster than USB 3.1. Only these USBs are compatible with Type C connections. These ports are full-duplex, meaning that data may be sent in both directions since USB is symmetrical.

4. USB4

USB4 (also known as USB 4.0) is a 2019 standard issued by the USB-IF in version 1.0. The USB4 protocol is built on the Thunderbolt 3 standard, which Intel Corporation submitted to the USB-IF. Its design may dynamically utilize a single high-speed connection with numerous end-device types, executing each transfer according to its data or application type.
The first products compatible with USB4 were Intel’s Tiger Lake processors, with more devices appearing around the end of 2020. This type of USB connection is yet to go mainstream.
Another way to understand the different types of USB is by classifying them based on the nature of the cable connection and physical design. Here are the key types of USB to note, continuing the previous list:

5. USB A

USB type-A connections, often known as type-A connectors, are among the most prevalent USB connectors. Consequently, they are also known as standard A connections. If laptops or desktop computers include a USB port (where USB devices may be plugged in), the port will likely be type A. Note that most recent Apple laptops (Macs) lack USB type-A connections.

6. USB B

Type B is square-shaped and smaller than type A. This is less prevalent than type-A; however, it may be found on computer components such as scanners, printers, external disk drives, etc. This type is mainly suitable for bulk data transfer connections. USB type-B is rarely found on laptops but may be prevalent in older desktop workstations, servers, and mainframes.

7. USB C

USB type-C is probably the most ubiquitous USB connection currently available. It fits readily into the tiniest peripherals we use today, such as cellphones, Bluetooth speakers, etc., due to its compact size. One of the numerous benefits of type-C over other current variations is that it supports “reverse plug orientation,” meaning that its plug may be inserted without regard to its orientation.
This means that you may charge your phone through your laptop or vice versa using type-C’s bi-directional power supply. The European Parliament Internal Market Committee (IMCO) has also confirmedOpens a new window that all devices launched in the EU will be mandatorily required to have USB-C charging capabilities. 

8. Lightning cables and ports (also built on USB technology)

Modern Apple devices, such as the iPhone and iPad, often include a separate USB connector: the Lightning cord. On one end of the cable is a narrow, rectangular connection, and on the other is a Type C connector. Similar to USB C, it is reversible or symmetrical, meaning it may be inserted either way. However, due to its design, the lightning connection cannot be utilized in any product or gadget other than Apple products.

9. Mini USB

This type of USB optimizes USB A or B connections for slightly older, portable devices. These are the miniature versions of the Type A and Type B USB connections. USB Mini is often found in portable cameras, gaming controllers, and older cell phones.

10. Micro USB

Again, the micro variant optimizes USB A or B for mobile devices – although for relatively newer ones. With the introduction of USB Type C, micro-USBs are now being phased out of newer high-end smartphone models. However, micro USB is still commonly used in inexpensive cell phones and other electronic devices, such as headphones, around the globe.
USB Micro B SuperSpeed is an additional variation of the micro USB standard. As the name indicates, this allows quicker data transmission than standard micro USB B ports. Therefore, these connections are often seen on external disk drives, where massive data transmission occurs frequently.
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Importance of USB Technology

For various reasons, USB is a foundational technology in the modern digital era for consumers and businesses alike.

1. Uses a single interface with easy scalability

USB’s adaptability eliminates the need for separate connection types and hardware specifications for each accessory. Additionally, the majority of personal computers feature three to four USB ports. If more USB ports are needed, USB hubs can be employed to add on external ports.

2. Minimizes space and power supply complexities

In comparison to older connections, USB sockets are smaller in size. Additionally, the USB interface was created right from the outset to function as a DC power source. Through its USB connector, any host device may provide the peripheral with 5V DC — between 500 mA (USB 1.0 and 2.0) and 900 mA (USB 3.0).

3. Does not need manual driver configurations

The host device’s operating system must only install the USB device driver once. After that, when the peripheral device is connected, the driver is immediately launched to set up the peripheral device. Typically, the device driver for any USB peripheral is loaded automatically the first time the peripheral is connected to the host.

4. Enables speed and reliability

USB offers multiple speed settings, making it more productivity-friendly and efficient. It provides speeds between 1.5Mbit/s to 5Gbit/s. 2013 saw the release of USB 3.1, which boosted the speed to 10Gbit/s. In addition, the USB protocol may detect data transmission errors and tell the transmitter to resend the data.

5. Saves costs

Due to the scalability of the manufacturing process and USB’s adaptability and popularity, it is now affordable to produce USB-supported products. Consequently, the components, connections, and cables are widely accessible and inexpensive. During “suspend mode,” the peripheral uses less than 500 microamperes for USB 2.0 and less than 2.5 milliamperes for USB 3.0, drastically reducing expenditures.

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Takeaway 

In the last two decades, USB has become the most widely accepted connectivity type for consumer devices. It has numerous applications for PC peripherals when working from home to extending mobile device storage. Organizations can leverage USB technology to add to their primary storage capabilities and to enable greater flexibility for employees. 

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