Data / Power

USB

USB (Universal Serial Bus) is the most widely used interface for connecting peripherals to computers and for charging devices. Since its introduction in 1996, USB has gone through multiple generations, each increasing speed and capability. USB replaced a variety of older interfaces including serial ports, parallel ports, and PS/2 connectors. Modern USB-C is becoming the universal standard connector for data, video, and power delivery.

Primary Use

Data Transfer, Charging & Peripheral Connectivity

Reference Image

USB cable and connector

Key Features

  • Multiple connector types: Type-A, Type-B, Mini, Micro, and Type-C
  • Supports data transfer, power delivery, and even video output (USB-C)
  • Color-coded connectors indicate speed generation (black=2.0, blue=3.0, teal=3.1 Gen 2, red=charging)
  • USB-C is reversible - no wrong way to plug it in
  • USB-A has a specific orientation - the USB trident logo faces up
  • Backward compatible across generations (speed limited to slower device)
  • Supports hot-swapping - connect/disconnect without restarting
  • USB Power Delivery (USB-PD) can deliver up to 240W of power over USB-C

Variants & Standards (10)

USB Type-A

The standard flat rectangular connector found on most computers

  • - Most common USB connector
  • - Found on host devices (computers, chargers)
  • - Not reversible - has correct orientation
USB Type-B

Square connector typically found on printers and scanners

  • - Square shape with beveled top corners
  • - Used on peripheral devices (printers, scanners, some external drives)
  • - Less common in modern devices
USB Mini-B

Smaller connector for portable devices (now mostly legacy)

  • - Trapezoidal shape
  • - Was common on older cameras, MP3 players, PS3 controllers
  • - Largely replaced by Micro-USB and USB-C
USB Micro-B

Thin, flat connector that was standard for mobile devices

  • - Very thin and flat
  • - Was the standard Android phone charging connector
  • - Still found on many budget devices and accessories
USB Type-C

The modern universal connector - reversible and versatile

  • - Reversible - no wrong orientation
  • - Supports USB4, Thunderbolt 3/4, DisplayPort Alt Mode
  • - Becoming mandatory in many regions (EU requires for phones)
  • - Can deliver up to 240W power
USB 2.0 480 Mbps (Hi-Speed)

Widely deployed standard, adequate for most peripherals

  • - Black connector color
  • - Sufficient for keyboards, mice, printers
USB 3.0 / 3.1 Gen 1 / 3.2 Gen 1 5 Gbps (SuperSpeed)

Major speed upgrade - also called SuperSpeed USB

  • - Blue connector color
  • - 10x faster than USB 2.0
  • - Additional pins in USB-A connector
USB 3.1 Gen 2 / 3.2 Gen 2 10 Gbps (SuperSpeed+)

Doubled SuperSpeed bandwidth

  • - Teal/dark blue connector
  • - Often USB-C connector
USB 3.2 Gen 2x2 20 Gbps

Dual-lane operation for maximum USB 3 speed

  • - USB-C connector only
  • - Uses two 10 Gbps lanes
USB4 40 Gbps (up to 80 Gbps with USB4 v2)

Latest USB standard based on Thunderbolt 3 protocol

  • - USB-C connector only
  • - Tunnels PCIe and DisplayPort
  • - Compatible with Thunderbolt 3
  • - Mandatory minimum 20 Gbps

Quick ID Tips

1 USB-A: Flat rectangular connector - by far the most recognizable USB plug
2 USB-B: Square-ish with beveled top corners - found on printers and scanners
3 Mini-USB: Small trapezoid shape - older cameras, controllers, GPS devices
4 Micro-USB: Very flat and wide, small tab - older phones and tablets
5 USB-C: Small oval/rounded rectangle - reversible, newest standard
6 Check connector color: Black = USB 2.0, Blue = USB 3.0, Teal = USB 3.1 Gen 2
7 The USB trident logo (fork symbol) is printed on most USB-A connectors

A+ Exam Notes

USB naming has been confusing - USB 3.0, 3.1 Gen 1, and 3.2 Gen 1 are ALL the same 5 Gbps speed
Color coding is key: Black = 2.0 (480 Mbps), Blue = 3.0 (5 Gbps)
USB-C is a CONNECTOR type, not a speed - USB-C can carry USB 2.0, 3.x, or USB4
Know the physical difference between all 5 connector types (A, B, Mini, Micro, C)
USB-A 3.0 connectors have additional pins deeper in the connector (visible as blue plastic)
Thunderbolt 3 and 4 use the USB-C connector but are NOT the same as USB
USB Power Delivery negotiates voltage/amperage - up to 48V/5A (240W) on USB-C

At a Glance

Type Data / Power
Variants 10
Key Features 8
Exam Tips 7