# USB 2 Standard-A plug

> a legacy USB plug that preceded USB-C (“A” indicating the host end)

**Wikidata**: [Q58050871](https://www.wikidata.org/wiki/Q58050871)  
**Source**: https://4ort.xyz/entity/usb-2-standard-a-plug

## Summary
The USB 2 Standard-A plug is a legacy USB plug that preceded USB-C, with "A" indicating the host end. It features a rectangular shape with a specific pinout configuration for data transfer and power delivery.

## Key Facts
- The USB 2 Standard-A plug is part of the USB Standard-A plug class and serves as the host end of USB connections.
- It was officially named USB 2.0 Standard-A plug according to USB documentation.
- The plug has four pins: VBUS (red, power), D- (white, data), D+ (green, data), and GND (black, ground).
- It was replaced by the USB-C plug as the modern standard for USB connections.
- The USB 2 Standard-A plug connects with USB 2 Standard-A receptacles and USB 3 Standard-A receptacles.
- It is distinct from other USB plugs like USB 2 Standard-B plug, USB 2 Micro-A plug, USB Mini-A plug, and USB 3 Standard-A plug.
- It is an instance of multiple classes: USB 2 Standard-A connector, USB 2 Standard plug, USB 2 Type-A plug, and USB Standard-A plug.
- It carries only USB 1-2 and power.

## FAQs
### Q: What is the USB 2 Standard-A plug used for?
A: The USB 2 Standard-A plug was the standard host connector used for connecting devices like computers and hubs to peripherals before USB-C.

### Q: How does the USB 2 Standard-A plug differ from USB-C?
A: The USB 2 Standard-A plug is a legacy, rectangular connector that can only carry USB 1-2 and power, while USB-C is a newer connector that replaced it.

### Q: Can a USB 2 Standard-A plug work with USB 3 devices?
A: Yes, a USB 2 Standard-A plug can connect to USB 3 Standard-A receptacles, though it will operate at USB 2 speeds since the plug itself only supports USB 1-2 standards.

### Q: What cables are compatible with USB 2 Standard-A plugs?
A: USB 2 Standard-A plugs connect to cables that terminate in USB 2 Standard-A receptacles or USB 3 Standard-A receptacles.

### Q: What does the "A" in USB 2 Standard-A indicate?
A: The "A" in USB 2 Standard-A indicates that it is the host end of the USB connection, typically used on computers and hubs rather than peripheral devices.

## Why It Matters
The USB 2 Standard-A plug was an important connector in the evolution of USB standards, serving as the host interface for countless devices. Its rectangular shape and pinout configuration provided a standardized way to connect peripherals to computers. Despite being replaced by USB-C, it remains a widely recognized standard that continues to be found in many devices. Its legacy demonstrates how technical standards can endure and maintain relevance even as technology advances.

## Notable For
- Being a legacy USB plug that preceded USB-C
- Establishing a standardized rectangular form factor that became widely recognized
- Implementing a simple yet effective four-pin design for data and power
- Being replaced by the USB 2 Type-C plug
- Carrying only USB 1-2 and power capabilities

## Body
### Physical Design
The USB 2 Standard-A plug features a distinctive rectangular shape that became one of the most recognized interfaces in computing. It was designed with a specific orientation that required users to align it correctly when connecting to devices.

### Pin Configuration
The plug implements a four-pin layout with standardized wire colors for easy identification:
- Pin 1 (red): VBUS - Power supply pin
- Pin 2 (white): D- - Negative differential data line
- Pin 3 (green): D+ - Positive differential data line
- Pin 4 (black): GND - Ground connection

### Standards Compliance
The USB 2 Standard-A plug is compatible with USB 1.1 and USB 2.0 specifications, supporting data transfer and power delivery.

### Connector Classifications
This plug belongs to multiple classification hierarchies:
- Instance of USB 2 Standard-A connector
- Instance of USB 2 Standard plug
- Instance of USB 2 Type-A plug
- Instance of USB Standard-A plug

### Evolution and Replacement
The USB 2 Standard-A plug has been largely replaced by the USB-C plug in newer devices, though it remains in use for backward compatibility. It carries only USB 1-2 and power, whereas USB-C offers more advanced capabilities.

## References

1. [Source](https://www.usb.org/document-library/usb-31-legacy-cable-and-connector-revision-10)
2. [Source](https://www.usb.org/document-library/usb-20-specification)