What is USB?

USB stands for "Universal Serial Bus" and is a standard for connecting devices such as computers, smartphones, peripheral devices and more.

The standard was first introduced in 1996 to facilitate compatibility between different devices. USB enables the transfer of data and power supply via a single cable. This made it possible to connect a variety of devices more easily and quickly, revolutionising the everyday lives of many users.

USB has established itself as an indispensable standard thanks to its versatility and ease of use. The user-friendly plug-and-play functionality ensures that devices can be connected without any prior technical knowledge. The universal compatibility makes it possible to connect devices from different manufacturers. USB is not only used for data transfer, but also for power supply, which is particularly essential for mobile devices such as smartphones and tablets.

USB connector types

USB plug types differ in their shape and area of application.

USB type C:

The modern, symmetrical plug that is both faster and more versatile. It enables higher data transfer rates and an improved power supply.

USB Type A:

This rectangular connector is the most commonly used type and can be found on computers, chargers and many other devices.

USB type B:

A square connector that is often used with larger peripheral devices such as printers or scanners.

I dati e l'energia per l'alimentazione vengono trasmessi insieme tramite un cavo al dispositivo finale (in genere telefoni IP, access point o telecamere IP). I cavi Ethernet sono a otto conduttori. Con i vecchi standard di rete, PoE utilizza due delle coppie di fili non utilizzate per la trasmissione dei dati. Con gli standard PoE più vecchi, vengono utilizzate due delle coppie di fili non utilizzate per la trasmissione dei dati. Con gli standard più recenti, che forniscono anche una maggiore potenza, l'alimentazione viene fornita tramite quattro coppie di fili.

Affinché l'elettricità possa fluire attraverso la rete, sono necessari dispositivi di distribuzione con capacità PoE, noti come Power Sourcing Equipment (PSE). Questi dispositivi possono essere suddivisi in due categorie: Switch PoE e iniettori PoE.

Uno switch PoE funziona come un normale distributore di rete, ma con la differenza che le porte forniscono anche l'alimentazione. A volte possono verificarsi problemi se i dispositivi finali collegati non sono compatibili con la tecnologia PoE. Si possono verificare sovratensioni e danni durante il funzionamento. Gli iniettori, invece, possono essere utilizzati in modo molto più flessibile.

L'iniettore PoE è collegato tra uno switch convenzionale e i partecipanti alla rete. I segnali di dati vengono quindi captati dal distributore e solo successivamente alimentati con potenza aggiuntiva. Questo ha il vantaggio di dover dotare di PoE solo le porte dello switch esistente che necessitano realmente dell'alimentazione supplementare.

USB-Standards

The various USB standards define the speed and functionality of the connection.

USB 1.0 / 1.1:

These early standards offered data rates of up to 12 Mb/s and were mainly used for simple peripheral devices.

USB 2.0:

With a speed of up to 480 Mb/s, this standard became widespread and enabled faster transmissions.

USB 3.2:

These standards increased the data rate to up to 20 Gb/s. USB 3.2 includes all previous versions of USB 3.0 and USB 3.1, but with new designations:

USB 3.2 Gen 1 (formerly USB 3.0 / USB 3.1 Gen 1):
- Speed: Up to 5 Gb/s.
- Often marketed as "SuperSpeed USB".
USB 3.2 Gen 2 (formerly USB 3.1 Gen 2):
- Speed: Up to 10 Gb/s.
- Is referred to as "SuperSpeed USB 10Gbps".
USB 3.2 Gen 2x2:
- Speed: Up to 20 Gb/s.
- Doubles the bandwidth by using two data channels (only possible with USB-C).
- Marketed as "SuperSpeed USB 20Gbps".

USB4 (based on Thunderbolt 3)

USB4 offers speeds of up to 40 Gb/s and is based on Thunderbolt 3 technology to enable maximum performance and flexibility via USB-C.

Introduced: 2019.
Speed: Up to 40 Gb/s.
Features: Uniform standard, high bandwidth, support for multiple protocols (e.g. DisplayPort, PCIe), full USB-C integration.

USB4 version 2.0

USB4 version 2.0 doubles the speed up to 80 Gb/s and ensures maximum bandwidth for demanding applications such as 8K displays and fast data transfers, while remaining fully backwards compatible.

Introduced: 2022.
Speed: Up to 80 Gb/s.
Features: Advances in data transfer and protocol integration, backwards compatibility with USB4, USB 3.2 and USB 2.0.

Technical basics

Data transmission

Data transfer via USB takes place in the form of data packets that are exchanged between the host (e.g. a computer) and the device. With USB 3.0 and higher, "SuperSpeed" modes were introduced, which enable a significant improvement in the transfer rate. These standards are particularly useful for applications such as transferring HD video or large amounts of data.

Power supply via USB

USB is not only used for data transfer, but also for power supply. The maximum available power has steadily improved with the standards:

USB 2.0: Supplies up to 2.5 watts of power (5 volts at 0.5 amps), sufficient for small devices.
USB 3.0: Increases the output to 4.5 watts and thus also supports more energy-intensive devices.
USB Power Delivery (PD): Provides scalable power of up to 100 watts and enables charging of laptops and other power-hungry devices.

Detailed information on the topic of USB Power Delivery

Power supply in the classic USB specifications (without USB PD)

Originally, current and voltage were defined in the USB standard before USB PD was introduced:

USB-Version	Voltage	Standard current	Maximum power
USB 2.0	5V	0,5A (500mA)	2,5W
USB 3.0 / 3.1	5V	0,9A (900mA)	4,5W
USB 3.2	5V	0,9A (900mA)	4,5W
USB 4	5V	0,9A (900mA)	4,5W

These values still apply to devices that do not support USB PD!

Stromversorgung mit USB Power Delivery (USB PD)

Mit USB PD wurde das Ladesystem flexibler und leistungsstärker:

USB PD-Version	Voltage	Maximum current	Maximum power
USB PD 1.0 (2012)	5V, 12V, 20V	2A (5V), 5A (12V, 20V)	100W
USB PD 2.0 & 3.0	5V, 9V, 15V, 20V	bis zu 5A	100W
USB PD 3.1 (2021)	5V, 9V, 15V, 20V, 28V, 36V, 48V	bis zu 5A	240W

USB PD does not replace the classic USB power values, but is an additional option for devices that support it.

USB in practice

Another very important aspect for an error-free and resilient PoE network is the selection of the correct cable; before installation, you should consider the cable length, the wire cross-section and the possible heating of the network cable. The higher the current flow, the more heat is generated by the resistance in the cable. This can impair data transmission. It is therefore important to check in advance what load the cable can withstand and how the heat generated can be safely dissipated. The higher the wire cross-section (AWG number), the more resilient the cable.

Development of new standards

The development of USB is progressing continuously. With USB4, a standard was introduced that supports data rates of up to 40 Gbit/s and offers improved efficiency at the same time. The integration of Thunderbolt technology makes USB4 particularly powerful and versatile, as it offers high compatibility and speed.

Trends

The future of USB lies in wireless transmission and integration into the Internet of Things (IoT). Wireless USB solutions offer new possibilities for more flexibility and user-friendliness. At the same time, USB is increasingly being used in smart home devices and other networked applications, further increasing its relevance.

USB articles from InLine

Discover the versatile USB range from InLine. Whether cables, adapters or USB hubs. InLine offers suitable solutions for all situations - even for older devices!

InLine® USB 3.0 Adapter Cable Type A female / Chassis Connector Type A, 0.20m

Route a USB-A port cleanly to the front panel Simple front panel mounting: Panel-mount socket with included screws for a secure hold. Tidy cable routing inside the enclosure: 0.20 m adapter length for short distances. Reliable connections: Gold-plate...

Item no.: 33445F