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USB | How it Works | Wiring Color Codes | Types | Versions | Uses

USB refers to cables, communication protocols, and connectors, required to communicate, power supply, and a link with computers & electronic devices. Moreover, it allows communication between devices and a PC. Basically, to link the computer to the electronic system, these buses come in handy for networking or power supply purposes. It is productive and reduces the workload in order to function of transferring data and supplies electrical power between various peripherals gadgets like printers, digital cameras, keyboards, scanners, flash drives, and external hard drives, etc. This also reduces the consumption of power that is best to store the data.



In the year 1994, a group of seven companies developed Universal Serial Bus(USB) namely Microsoft, Compaq, Intel, Nortel, DEC, IBM and NEC. The Universal Serial Bus was designed to simplify and make the work comfortable for the user in connecting external devices. Windows and Mac considered it as a very useful tool.

Before the use of Universal Serial Bus, the ports were used to plug into devices and computers to transfer the data. Every peripheral device used their own individual port to connect with the computer. Due to high level of incompatibility and issues in using multiple interfaces, the need of a technology like the Universal Serial Bus emerged. Also, the transfer of data between the serial and parallel ports was quite slow and ranged between 100-450 kbs per second.

Locations of USB Ports

In all the modern computers, there will be at least one Universal Serial Bus port. Below are the exact locations where we can find these ports –

  • Desktop Computers – In this computer, it usually has two- four ports in the front and two- eight ports at the backside.

Computer USB Ports

  • Laptop Computers – In this computer, there are one and four ports on the laptop’s left, right and at both the sides.

Laptop USB Ports

  • Tablet Computers – The connection with tablet is in the charging port and it is commonly Micro-USB and sometimes USB-C. There are few tablets which has additional  ports.

Tablet USB Port

  • Smartphone – Unlike tablets, the port on the smartphones are used for both charging and transferring the data in the form of USB-C or Micro-USB.

Smartphone USB Port

How USB Works?

Universal Serial Bus is a standardized technology that allows devices to connect and communicate with each other. It provides a common interface for data transfer, power supply, and peripheral device connectivity. Here’s a description of how it works:

How USB Works


USB uses various types of connectors, such as Type-A, Type-B, Micro, Mini, and Type-C. These connectors have specific shapes and pin configurations to ensure proper connectivity between devices.

Host and Peripheral Devices

In USB, there are two primary roles: host and peripheral. The host device, usually a computer or a smartphone, acts as the main controller and manages the connection. Peripheral devices, such as keyboards, printers, or external hard drives, connect to the host device and receive instructions from it.

Data Transfer

USB supports simultaneous data transfer in both directions. The host and peripheral devices communicate using a client-server model. The host initiates the communication and sends commands or data to the peripheral device, which responds accordingly.

USB Protocol

It uses a layered protocol known as the Universal Serial Bus protocol stack. The stack consists of four layers: the physical layer, data link layer, transaction layer, and the application layer.

Physical Layer

This layer handles the electrical and physical aspects of the Universal Serial Bus connection, including the voltage levels and signal transmission.

Data Link Layer

The data link layer manages the reliable transmission of data packets over the Universal Serial Bus connection. It ensures error detection and correction, as well as flow control.

Transaction Layer

The transaction layer organizes the data into packets and manages their delivery between the host and peripheral devices. It handles the sequencing and buffering of data packets.

Application Layer

The application layer defines the protocols and specifications for specific Universal Serial Bus device classes, such as keyboards, mice, printers, storage devices, and more. These specifications allow devices to communicate with the host device using standardized commands and data formats.

Power Supply

Universal Serial Bus also provides power supply capabilities, allowing peripheral devices to draw power from the host device. The host device determines the amount of power to allocate to each connected peripheral based on the device’s power requirements.


USB incorporates the Plug-and-Play feature, which means that devices can be connected or disconnected from the USB port while the system is running without the need for restarting or reconfiguring the system. This enables easy and convenient device connectivity and use.

USB Wiring Color Coding

USB Wiring Diagram

The wiring color coding refers to the standardized color scheme used for the different wires within a USB cable. The color coding is designed to ensure consistency and proper connections between USB devices. Here is the typical color coding for USB cables:

    • Red: VCC (Power)
    • White: D- (Data Minus)
    • Green: D+ (Data Plus)
    • Black: GND (Ground)

Connection with Computer

To connect it with the computer system, just insert the USB device into the USB port. It will automatically identify the device after it is inserted and user can work on it further. After the device is inserted to the computer, rebooting is not required.

Types of Universal Serial Bus

There are different types of the Universal Serial Bus available-


Micro Universal Serial Bus

It is a type of Universal Serial Bus connector commonly used for connecting and charging various devices such as smartphones, tablets, digital cameras, and other portable electronics. It was developed as a smaller and more compact alternative to the standard  Type-A connector.

One of the notable features of Micro USB is its reversible plug orientation, which means that it can be inserted into the device’s port in either direction, eliminating the need to align the connector in a specific way. This feature was a significant improvement over the previous USB connector types, such as Mini USB, which required proper alignment for insertion.

Mini Universal Serial Bus

It is a type of Universal Serial Bus connector that was commonly used before the introduction of Micro and Type-C connectors. It provided a compact and standardized interface for connecting and charging various devices, including digital cameras, MP3 players, external hard drives, and other portable electronics.

Mini USB was a widely used USB connector type before the introduction of Micro and Type-C. It provided a standardized interface for data transfer and charging but lacked the reversibility and compactness of its successors. As technology evolved, Mini USB has been largely replaced by more advanced and versatile USB connector types.

Unlike Micro and Type-C, Mini USB connectors had a specific orientation, requiring users to align the connector properly before insertion.

Type – A 
Type-A connectors are primarily used for data transfer and power supply purposes. It is designed to connect to the corresponding Type-A receptacle on peripheral devices such as computers, laptops, gaming consoles, and USB hubs.
These connectors are not reversible, meaning they can only be inserted in one specific orientation.

Type – B 

It refers to a specific type of Universal Serial Bus connector known as the USB Type-B connector. It is commonly used as a peripheral connector to establish a connection between a device and a host device or computer.

These connectors are not reversible, meaning they can only be inserted in one specific orientation.

Type – C

It often referred to simply as USB-C, is a specific type of Universal Serial Bus connector that has gained widespread popularity in recent years.

USB Type-C has become the standard connector on many modern devices, including smartphones, tablets, laptops, and peripheral devices. It has also gained widespread adoption in the tech industry due to its flexibility and potential for creating thinner and more compact devices.

It is a small, reversible USB connector that offers faster data transfer speeds, higher power delivery capabilities, and versatility in supporting various protocols.

Versions of Universal Serial Bus

Below are some of the details of the various versions-

Universal Serial Bus 4 

Announced in 2019, is based on the Thunderbolt 3 protocol. It offers even higher data transfer speeds, reaching up to 40 Gbps (SuperSpeed+). USB4 also supports multiple simultaneous data and display protocols over a single USB Type-C cable. USB4 maintains backward compatibility with previous USB generations.

Universal Serial Bus 3.2 

Released in 2017, introduced new multi-lane operation modes for higher data transfer speeds. It supports two-lane operation, enabling data rates of up to 10 Gbps per lane (20 Gbps in total) and four-lane operation for up to 10 Gbps per lane (40 Gbps in total). It maintains backward compatibility with previous USB generations.

Universal Serial Bus 3.2 Gen 2

Introduced in 2013, further improved the data transfer speed to 10 Gbps (SuperSpeed+). It offered faster and more efficient performance compared to USB 3.1 Gen 1. USB 3.1 Gen 2 is backward compatible with earlier USB versions.

Universal Serial Bus 3.0 and 3.1 Gen 1

Introduced in 2008, brought substantial enhancements in data transfer speed, reaching up to 5 Gbps (SuperSpeed). USB 3.0 was backward compatible with USB 2.0 devices.

Universal Serial Bus 2.0

Released in 2000, USB 2.0 became the most widely adopted version for many years. It offered significant improvements over the previous versions, with data transfer rates of up to 480 Mbps (High-Speed). USB 2.0 also introduced backward compatibility with USB 1.x devices.

Universal Serial Bus 1.0 and 1.1

These were the initial versions, introduced in 1996 and 1998, respectively. USB 1.0 had a maximum data transfer rate of 1.5 Mbps (Low-Speed) and 12 Mbps (Full-Speed), while USB 1.1 improved the data transfer rate to 12 Mbps (Full-Speed).

Characteristics of Universal Serial Bus

  • To a single USB host controller, a maximum of 127 peripherals can be connected.
  • It has a maximum speed of up to 480 Mbps.
  • An individual USB cable’s length can be up to an extent of 5 meters without a hub and 40 meters with hub.
  • It acts like a “plug and play” device.
  • It can get power by its own supply or from a computer.
  • Few USB devices will automatically turn into “sleep mode” as and when the computer turns into power saving mode.

Uses of Universal Serial Bus

In today’s generation, various Universal Serial Bus connects to the computer system. Below are some of them in common –

  • Digital Camera
  • Gamepad
  • Headset
  • iPod and Mp3 players
  • Keyboard
  • Mouse
  • Printer
  • Scanner
  • Speakers
  • Thumb drive
  • Webcams
  • Tablets
  • External Drive


  • It consumes less power.
  • It is less expensive.
  • Every device that has USB port will fits in with USB.
  • It can be of various sizes and their connections are also of various ways.
  • Acceptable data rate for many of the applications.
  • Robust connector system.


  • Data transfer is not fast when compared to other systems.
  • It does not include broadcast function. Only single messages can be exchanged between the host and the peripheral.
  • It has its own limit in performance and functionalities.
  • Use of USB logo on the product would require annual fees and membership in any of the organization.

They provide a realistic alternative to the current problem of configuring new peripherals to use with the personal computers. One of the main advantages is the easy use for the user who has to simply plug in the device into any available port for the device to immediately become available to the required software. However, one drawback for the consumer is likely to be the cost of upgrading their systems in order to use them. In addition to this, USB capable computers still supports traditional system and hence there will be no problem with compatibility of older hardware with such a computer. Therefore, there is a chance for people to purchase Universal Serial Bus hardware and thus for manufacturers to build them.

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Chakrasthitha is a B.E (Medical Electronics) and has work experience in MatLab and Lab View Software as Design Engineer at BCS innovations and Manipal hospital as Biomedical Engineer. She is an author, editor and partner at Electricalfundablog.


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