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

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Written By Devansh Vijay

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The universal serial bus (USB), is a standard that describes the specifications of cables, ports, and protocols used to enable easy and universally recognized connectivity between a host device and a peripheral device. 

USB (Universal Serial Bus) can be used by cables, ports, and protocols to allow universally accepted device–peripheral connections.

This article will explain what USB is and which types it is.

What is USB (Universal Serial Bus), and How Can it Help You?

The universal serial bus (or USB) is a method to connect peripheral devices and computers. A PC used to have one or two serial connections.

There was also a parallel port and keyboard and mouse connectors. In some cases, there was even a joystick port.

As a simpler way to connect peripherals, the USB (Universal Serial Bus) standard was created in the mid-1990s. It was developed by several American companies such as IBM, Intel, and Microsoft Corporation.

This port was a standard way to connect various devices and provided significant speed advantages over other options.

At first, USB (Universal Serial Bus) technology acceptance was slow.

  • Before USB-capable peripherals became available, computer manufacturers were slow to add the ports to their systems.
  • Manufacturers of peripheral devices were also reluctant to promote USB products before USB ports became ubiquitous on newer computers.
  • Operating systems were not capable of supporting the tech when it was first launched.

It was a breakthrough when the first model of Apple Inc.'s iMac arrived in 1998. Apple's iMac was a well-received model that only had USB (Universal Serial Bus) connections.

This forced other manufacturers to follow the lead. The majority of peripheral devices including scanners, printers, keyboards, and scanners have used USB since then.

Acceptance of the standard spurred the development of new technologies, such as portable memory sticks (popularly known as USB storage), which eventually replaced floppy disks.

The USB Implementers Forum (USB-IF) has now a standardized USB design. This forum is made up of organizations that support and promote USB. The USBIF not only endorses USB but also maintains and enforces compliance programs.

How does USB (Universal Serial Bus) Work?

The computer's bus is a network made up of cables that transport data between its internal components and external devices. It's a metaphor for an electronic busbar that distributes electricity over large, energy-hungry places such as factories.

Before the advent of a USB, every peripheral device could be connected to a computer via the port it was built.

As the number of peripheral devices grew, a standard method for exchanging data between the primary host and various devices became necessary. The USB was born.

A peripheral device connected to a host machine via USB (Universal Serial Bus) will be automatically identified and a driver installed by the host machine.

USB transfers data between two devices in small, bite-sized amounts known as "packets". Each packet contains a predetermined number of bytes (a digital unit).

This information may include information such as the origin and destination of the material and any anomalies.

You Can Break Down the Workings of a USB (Universal Serial Bus) as Follows:

Data transfer in large quantities: This type is used by digital scanners and printers to transfer large amounts of data. This is a common low-priority transfer and is not time-sensitive. If there are many USB (Universal Serial Bus) devices attached to the host machine, it may delay the operation.

Minimal packets for critical connection: This feature allows peripheral systems such as keyboards and mice, to transmit small amounts of data. These transmissions can be used for small but important requirements.

The remote device makes requests and waits for the host to inquire about the exact data it needs. If the first request fails, the requests will be resubmitted. The USB (Universal Serial Bus)will inform you if there have been any changes to the device's status.
Control packet transfer for USB management: This data transmission is used in setting up and managing USB devices. After submitting a request to the device the host, data transmission follows. Status checks can also be performed using control transfer. Only one control request can ever be processed at a time.

Real-time data transfer in the isochronous format: This is for audio, video, and other real-time data. Transmission errors can occur during transmission. However, the transmission will not be paused to submit the packets again.

These transfers can sometimes include situations in which the integrity of the data may not be crucial.

For example, the transmission of audio parts in a Voice Over Internet Protocol (VoIP), call that the listener might not recognize. These components should be excluded rather than resending data which could cause audio glitches.

The host keeps track of all interrupt and isochronous devices, so it can keep an eye on how many devices are using the bandwidth.

They may consume up to 90% of available bandwidth together, which is 480 megabits/second for USB standard or 4.8 gigabits/second with USB 3.0.

Once 90% is consumed, the host blocks access to any other interrupt or isochronous devices. Any bandwidth left over for control packets or bulk transfer packets is used (which is always 10%). You cannot use multiple USB connections to transfer data at once.

What is the Working Principle of USB (Universal Serial Bus) Cables?

The USB port is an interface standard for connecting cables to computers and other consumer electronics devices. This port can be connected to a special wire, the USB cable. The cable has one end that connects to the host, and the other to the peripheral. Depending on the type of USB, the two ends might not be symmetrical.

USB cables can transmit power as well as information. Two types of wires are required for any USB cable to transmit power and information. One set transmits data signals while the other transports current.

The standard USB 2.0 connection has four metal strips. The power supply's negative and positive terminals are located on the two outermost strips.

Two of the center strips are for data transmission. The latest USB 3.0 connection allows for the addition of data-carrying strips to increase the data transmission speed. USB 3.0 is faster thanks to four additional signaling lines.

USB (Universal Serial Bus): Key Features

The following are supported by universal serial bus connections, which can be enabled via USB ports or USB cables

Hot Swapping

One of the most important features of the USB is hot swapping. This allows for the replacement or removal of a device without the need to restart or interrupt the system.

When installing or uninstalling an older device, the PC must be restarted. Rebooting was the first step to avoid electrostatic discharge (ESD), which is an unintentional electrical current that can cause severe damage to fragile electronic devices.

This is unnecessary with USB. Hot swapping can be fault-ruggedized which means it can continue to function despite hardware failure.

Direct Current Transfer

The use of direct current (DC) is another aspect of USB (Universal Serial Bus). Although several devices can be connected to DC via a USB power connector, they do not transmit data. You can find USB speakers, small refrigerators, and keyboard lamps as well as USB-based chargers for your devices.

Multiple Contact Points

Each USB connection has at least four contacts. These are used for power, ground, and two data wires (D+ and D-). USB 3.0 connectors have five contacts.

The USB connection can transmit 5V at a maximum current limit of 500mA. Only one direction can be used for the USB connection. You can force a wrong connection. This could lead to devise damage.

Protection and Shielding

Insulated USB connections provide a metal casing that is not part of the circuit. This is essential for maintaining signal integrity in an electrically "busy", environment. To prevent damage to the cable or electrical connection, all USB cables are protected at the connector end with plastic.

There are 10 Types of USB

The four generations of USBs or the type and type of cables they use can be used to classify them. Let's first take a look at the four versions of USB that have evolved.

1. Original USB (Universal Serial Bus)

As explained previously, before USBs, systems used parallel and serial ports. Apple, Microsoft, and Intel worked together to create a universal device that could connect multiple external sources to a computer without the need to reboot.

This was the original generation that was available in the 1990s.

2. USB 2.0

The widespread adoption of USB 2.0 was a result of its popularity in 2000. Version 2.0 was faster than version 1.1. USB 2.0 was able to transfer data at a rate of up to 480 megabits per sec, which is 40 times faster than USB 1.1. USB 2.0 could be used with any USB 1.1 port, and vice versa.

3. USB 3.0, USB 3.1, or 3.2

USB 3.0 was the first device to efficiently transport high-definition videos. The device was also known as SuperSpeed USB. It had transfer speeds up to 5 gigabits per sec or around 5,120 megabits each second.

USB 3.0 was not as popular as USB 1.0 and its successors were much more well-received.
Chromebooks and Macbooks were the first laptops that adopted the 2014-introduced USB 3.1. USB 3.1's maximum transmission speed was 10 gigabits per sec.

Three years later, USB 3.2 launched with transmission speeds of 20 gigabits/second, which was two times faster than USB 3.1. These USBs only work with Type C connections. These ports can send data in both directions because they are full-duplex.

4. USB4

The USB-IF issued the 2019 standard USB4 in version 1.0. The Thunderbolt 3 standard was submitted by Intel Corporation to the USB-IF. This is the basis of the USB4 protocol.

It may use a single high-speed connection with multiple end devices, dynamically executing each transfer according to its data type or application type.

Intel's Tiger Lake processors were the first to be compatible with USB4. More devices will follow by 2020. This type of USB connection has yet to become mainstream.

You can also classify USBs based on their physical design and cable connections. This will help you understand the differences between them. These are the main types of USBs you should be aware of, in continuation to the previous list.

5. USB A

The most common USB (Universal Serial Bus) connectors are USB type A connections. They have also known by the standard A connector.

The USB port on laptops and desktop computers that have a USB (Universal Serial Bus) port (for USB devices to be plugged into), will type A. Not all Apple Macs have USB type-A connections.

6. USB B

Type B is smaller and squarer than type A. It is less common than type A, but it can be found on components like scanners, printers, and external disk drives.

This type is best suited for bulk data transfer connections. Although USB type-B is not often found in laptops, it may be present in older workstations, servers, and mainframes.

7. USB C

The most common USB connection is USB type-C. Because of its small size, it fits easily into even the smallest peripherals such as smartphones, Bluetooth speakers, and so on.

Type-C has many advantages over current varieties. It supports "reverse connector orientation", which means that the plug can be inserted regardless of its orientation.

You can charge your phone via your laptop using type-C's bidirectional power supply. Opens a new window. The European Parliament Internal Market Committee has also confirmed that all devices manufactured in the EU must have USB-C charging capabilities.

8. Lightning Cables and Ports are Also Made Using USB Technology

The Lightning cord is a separate USB connector that Apple devices such as the iPhone or iPad often have. The cable has a narrow rectangular connector on one end and a Type C connector on the other.

It is similar to USB (Universal Serial Bus) C and can be used in either a reversible or symmetrical way. The lightning connector cannot be used in any other product or gadget than Apple products due to its design.

9. Mini USB (Universal Serial Bus)

This USB type optimizes USB A and B connections for older, portable devices. These are miniature versions of Type A and Type B USB connectors. USB Mini can be found in older phones, portable cameras, gaming controllers, and other devices.

10. Micro USB (Universal Serial Bus)

The micro variant optimizes USB A and B for mobile devices, although it is only for older models. Micro-USBs will be phased out of high-end smartphone models with USB (Universal Serial Bus) Type C.

Micro USB (Universal Serial Bus) can still be found in low-cost smartphones and other electronic devices around the world, including headphones.

USB Micro B SuperSpeed, an extra variant of the micro USB (Universal Serial Bus) standard, is available. This allows faster data transmission than standard micro USB B ports. These connections are frequently found on external drives that receive large amounts of data.


USB (Universal Serial Bus) has been the most popular connectivity type for consumer devices for the past 20 years. There are many uses for USB (Universal Serial Bus) technology, from personal computer peripherals to expanding mobile device storage.

To increase their primary storage capacity and give employees greater flexibility, organizations can use USB (Universal Serial Bus) technology.

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