Media Transfer Protocol (MTP) was designed by Microsoft to give higher-level access to a device's filesystem than USB mass storage, at the level of files rather than disk blocks. It also has optional DRM features. MTP was designed for use with portable media players, but it has since been adopted as the primary storage access protocol of the Android operating system from the version 4.1 Jelly Bean as well as Windows Phone 8 (Windows Phone 7 devices had used the Zune protocol—an evolution of MTP). The primary reason for this is that MTP does not require exclusive access to the storage device the way UMS does, alleviating potential problems should an Android program request the storage while it is attached to a computer. The main drawback is that MTP is not as well supported outside of Windows operating systems.

USB connector types multiplied as the specification progressed. The original USB specification detailed standard-A and standard-B plugs and receptacles. The connectors were different so that users could not connect one computer receptacle to another. The data pins in the standard plugs are recessed compared to the power pins, so that the device can power up before establishing a data connection. Some devices operate in different modes depending on whether the data connection is made. Charging docks supply power, and do not include a host device or data pins, allowing any capable USB device to charge or operate from a standard USB cable. Charging cables provide power connections but not data. In a charge-only cable, the data wires are shorted at the device end; otherwise, the device may reject the charger as unsuitable.

In the current standard, the USB-C connector replaces the many various connectors for power (up to 240 W), displays (e.g. DisplayPort, HDMI), and many other uses, as well as all previous USB connectors.

The USB 3.0 standard does not directly specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG 26 wires the maximum practical length is 3 meters (9 ft 10 in).[94]

The host controller directs traffic flow to devices, so no USB device can transfer any data on the bus without an explicit request from the host controller. In USB 2.0, the host controller polls the bus for traffic, usually in a round-robin fashion. The throughput of each USB port is determined by the slower speed of either the USB port or the USB device connected to the port.

The USB 1.1 standard specifies that a standard cable can have a maximum length of 5 meters (16 ft 5 in) with devices operating at full speed (12 Mbit/s), and a maximum length of 3 meters (9 ft 10 in) with devices operating at low speed (1.5 Mbit/s).[91][92][93]

A USB device may consist of several logical sub-devices that are referred to as device functions. A composite device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function). An alternative to this is a compound device, in which the host assigns each logical device a distinct address and all logical devices connect to a built-in hub that connects to the physical USB cable.

The USB 3.0 specification introduced an A-to-A cross-over cable without power for connecting two PCs. These are not meant for data transfer but are aimed at diagnostic uses.

This section describes the power distribution model of USB that existed before Power-Delivery (USB-PD). On devices that do not use PD, USB provides up to 7.5 W through Type-A and Type-B connectors, and up to 15 W through USB-C. All pre-PD USB power is provided at 5 V.

Low-power and high-power devices remain operational with this standard, but devices implementing SuperSpeed can provide increased current of between 150 mA and 900 mA, by discrete steps of 150 mA.[30]: 9–9

USB 3.1, released in July 2013 has two variants. The first one preserves USB 3.0's SuperSpeed architecture and protocol and its operation mode is newly named USB 3.1 Gen 1,[32][33] and the second version introduces a distinctively new SuperSpeedPlus architecture and protocol with a second operation mode named as USB 3.1 Gen 2 (marketed as SuperSpeed+ USB). SuperSpeed+ doubles the maximum signaling rate to 10 Gbit/s (later marketed as SuperSpeed USB 10 Gbps by the USB 3.2 specification), while reducing line encoding overhead to just 3% by changing the encoding scheme to 128b/132b.[32][34]

... a connection-oriented, tunneling architecture designed to combine multiple protocols onto a single physical interface so that the total speed and performance of the USB4 Fabric can be dynamically shared.[2]

USB bridge cables have become less important with USB dual-role-device capabilities introduced with the USB 3.1 specification. Under the most recent specifications, USB supports most scenarios connecting systems directly with a Type-C cable. For the capability to work, however, connected systems must support role-switching. Dual-role capabilities requires there be two controllers within the system, as well as a role controller. While this can be expected in a mobile platform such as a tablet or a phone, desktop PCs and laptops often will not support dual roles.[95]

UAC 3.0 primarily introduces improvements for portable devices, such as reduced power usage by bursting the data and staying in low power mode more often, and power domains for different components of the device, allowing them to be shut down when not in use.[74]

The USB 3.2 specification[7] added a second lane to the Enhanced SuperSpeed System besides other enhancements so that the SuperSpeedPlus USB system part implements the Gen 1×2, Gen 2×1, and Gen 2×2 operation modes. However, the SuperSpeed USB part of the system still implements the one-lane Gen 1×1 operation mode. Therefore, two-lane operations, namely USB 3.2 Gen 1×2 (10 Gbit/s) and Gen 2×2 (20 Gbit/s), are only possible with Full-Featured USB-C. As of 2023, they are somewhat rarely implemented; Intel, however, started to include them in its 11th-generation SoC processor models, but Apple never provided them. On the other hand, USB 3.2 Gen 1(×1) (5 Gbit/s) and Gen 2(×1) (10 Gbit/s) have been quite common for some years.

The different A and B plugs prevent accidentally connecting two power sources. However, some of this directed topology is lost with the advent of multi-purpose USB connections (such as USB On-The-Go in smartphones, and USB-powered Wi-Fi routers), which require A-to-A, B-to-B, and sometimes Y/splitter cables.

For a host providing power to devices, USB has a concept of the unit load. Any device may draw power of one unit, and devices may request more power in these discrete steps. It is not required that the host provide requested power, and a device may not draw more power than negotiated.

ToxicityAquatic toxicity:No data availablePersistence and degradabilityNo data availableBioaccumulative potentialNo data availableMobility in soilNo data availableEcotoxical effects:Remark:Very toxic for aquatic organismsAdditional ecological information:Do not allow material to be released to the environment without official permits.Do not allow product to reach groundwater, water courses, or sewage systems, even in small quantities.Danger to drinking water if even extremely small quantities leak into the ground.Also poisonous for fish and plankton in water bodies.May cause long lasting harmful effects to aquatic life.Avoid transfer into the environment.Very toxic for aquatic organismsResults of PBT and vPvB assessmentPBT: N/AvPvB: N/AOther adverse effectsNo data available

A group of seven companies began the development of USB in 1995:[16] Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration of all devices connected to USB, as well as permitting greater data transfer rates for external devices and plug and play features.[17] Ajay Bhatt and his team worked on the standard at Intel;[18][19] the first integrated circuits supporting USB were produced by Intel in 1995.[20]

When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device. The signaling rate of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host and the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.

Description of first aid measuresGeneral informationImmediately remove any clothing soiled by the product.Remove breathing apparatus only after contaminated clothing has been completely removed.In case of irregular breathing or respiratory arrest provide artificial respiration.If inhaled:Supply patient with fresh air. If not breathing, provide artificial respiration. Keep patient warm.Seek immediate medical advice.In case of skin contact:Immediately wash with soap and water; rinse thoroughly.Seek immediate medical advice.In case of eye contact:Rinse opened eye for several minutes under running water. Consult a physician.If swallowed:Do not induce vomiting; immediately call for medical help.Information for doctorMost important symptoms and effects, both acute and delayedNo data availableIndication of any immediate medical attention and special treatment neededNo data available

Extinguishing mediaSuitable extinguishing agentsProduct is not flammable. Use fire-fighting measures that suit the surrounding fire.Special hazards arising from the substance or mixtureIf this product is involved in a fire, the following can be released:Selenium dioxide (SeO2)Metal oxide fumeAdvice for firefightersProtective equipment:Wear self-contained respirator.Wear fully protective impervious suit.

USB4 2.0 with 80 Gbit/s speeds was to be revealed in November 2022.[46][47] Further technical details were to be released at two USB developer days scheduled for November 2022.[48][needs update]

The USB standard also provides multiple benefits for hardware manufacturers and software developers, specifically in the relative ease of implementation:

The Universal Serial Bus was developed to simplify and improve the interface between personal computers and peripheral devices, such as cell phones, computer accessories, and monitors, when compared with previously existing standard or ad hoc proprietary interfaces.[12]

GHS06 GHS08Signal word: DangerHazard statementsH301+H331 Toxic if swallowed or if inhaled.H373 May cause damage to the central nervous system, the liver and the digestive system through prolonged or repeated exposure.Route of exposure: Oral,Inhalative.Precautionary statementsP273 Avoid release to the environment.P270 Do not eat, drink or smoke when using this product.P309 IF exposed or if you feel unwell:P310 Immediately call a POISON CENTER or doctor/physician.P302+P352 IF ON SKIN: Wash with plenty of soap and water.P501 Dispose of contents/container in accordance with local/regional/national/international regulations.WHMIS classificationD1A - Very toxic material causing immediate and serious toxic effectsClassification systemHMIS ratings (scale 0-4)(Hazardous Materials Identification System) HEALTH FIRE REACTIVITY20 1Health (acute effects) = 2Flammability = 0Physical Hazard = 1Other hazardsResults of PBT and vPvB assessmentPBT: N/AvPvB: N/A

USB4 is based on the Thunderbolt 3 protocol.[43] It supports 40 Gbit/s throughput, is compatible with Thunderbolt 3, and backward compatible with USB 3.2 and USB 2.0.[44][45] The architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application.

eSATAp support can be added to a desktop machine in the form of a bracket connecting the motherboard SATA, power, and USB resources.

ReactivityNo data availableChemical stabilityStable under recommended storage conditions.Thermal decomposition / conditions to be avoided:Decomposition will not occur if used and stored according to specifications.Possibility of hazardous reactionsNo dangerous reactions knownConditions to avoidNo data availableIncompatible materials:BasesOxidizing agentsHazardous decomposition products:Hydrogen selenideSelenium dioxide (SeO2)Metal oxide fume

Classification of the substance or mixtureClassification according to Regulation (EC) No 1272/2008GHS06 Skull and crossbonesAcute Tox. 3 H301 Toxic if swallowed.Acute Tox. 3 H331 Toxic if inhaled.GHS08 Health hazardSTOT RE 2 H373 May cause damage to the central nervous system, the liver and the digestive system through prolonged or repeated exposure. Route of exposure: Oral, Inhalative.Hazards not otherwise classifiedNo data availableLabel elementsLabelling according to Regulation (EC) No 1272/2008The substance is classified and labeled according to the CLP regulation.Hazard pictograms

DisplayLink is a technology which allows multiple displays to be connected to a computer via USB. It was introduced around 2006, and before the advent of Alternate Mode over USB-C it was the only way to connect displays via USB. It is a proprietary technology, not standardized by the USB Implementers Forum and typically requires a separate device driver on the computer.

When a host starts a data transfer, it sends a TOKEN packet containing an endpoint specified with a tuple of (device_address, endpoint_number). If the transfer is from the host to the endpoint, the host sends an OUT packet (a specialization of a TOKEN packet) with the desired device address and endpoint number. If the data transfer is from the device to the host, the host sends an IN packet instead. If the destination endpoint is a uni-directional endpoint whose manufacturer's designated direction does not match the TOKEN packet (e.g. the manufacturer's designated direction is IN while the TOKEN packet is an OUT packet), the TOKEN packet is ignored. Otherwise, it is accepted and the data transaction can start. A bi-directional endpoint, on the other hand, accepts both IN and OUT packets.

HandlingPrecautions for safe handlingKeep container tightly sealed.Store in cool, dry place in tightly closed containers.Ensure good ventilation at the workplace.Open and handle container with care.Information about protection against explosions and fires:No data availableConditions for safe storage, including any incompatibilitiesRequirements to be met by storerooms and receptacles:No special requirements.Information about storage in one common storage facility:Store away from oxidizing agents.Further information about storage conditions:Keep container tightly sealed.Store in cool, dry conditions in well-sealed containers.Specific end use(s)No data available

Released in January 1996, USB 1.0 specified signaling rates of 1.5 Mbit/s (Low Bandwidth or Low Speed) and 12 Mbit/s (Full Speed).[21] It did not allow for extension cables, due to timing and power limitations. Few USB devices made it to the market until USB 1.1 was released in August 1998. USB 1.1 was the earliest revision that was widely adopted and led to what Microsoft designated the "Legacy-free PC".[22][23][24]

InterChip USB is a chip-to-chip variant that eliminates the conventional transceivers found in normal USB. The HSIC physical layer uses about 50% less power and 75% less board area compared to USB 2.0.[105] It is an alternative standard to SPI and I2C.

After the specification was made royalty-free and custodianship of the Thunderbolt protocol was transferred from Intel to the USB Implementers Forum, Thunderbolt 3 has been effectively implemented in the USB4 specification – with compatibility with Thunderbolt 3 optional but encouraged for USB4 products.[124]

USB4 particularly supports the tunneling of the Thunderbolt 3 protocols, namely PCI Express (PCIe, load/store interface) and DisplayPort (display interface). USB4 also adds host-to-host interfaces.[2]

The USB Device Class Definition for MIDI Devices transmits Music Instrument Digital Interface (MIDI) music data over USB.[117] The MIDI capability is extended to allow up to sixteen simultaneous virtual MIDI cables, each of which can carry the usual MIDI sixteen channels and clocks.

Modifications to the USB specification have been made via engineering change notices (ECNs). The most important of these ECNs are included into the USB 2.0 specification package available from USB.org:[27]

While the USB spec originally described asynchronous mode being used in "low cost speakers" and adaptive mode in "high-end digital speakers",[86] the opposite perception exists in the hi-fi world, where asynchronous mode is advertised as a feature, and adaptive/synchronous modes have a bad reputation.[87][88][80] In reality, all types can be high-quality or low-quality, depending on the quality of their engineering and the application.[84][72][89] Asynchronous has the benefit of being untied from the computer's clock, but the disadvantage of requiring sample rate conversion when combining multiple sources.

Devices that draw more than one unit are high-power devices (such as typical 2.5-inch hard disk drives). USB up to 2.0 allows a host or hub to provide up to 2.5 W to each device, in five discrete steps of 100 mA, and SuperSpeed devices (USB 3.0 and up) allows a host or a hub to provide up to 4.5 W in six steps of 150 mA. USB-C supports high-power devices with up to 7.5 W, in six steps of 250 mA. Full-featured USB-C can support up to 15 W.

The Type-A and Type-B connectors came in Standard, Mini, and Micro sizes. The standard format was the largest and was mainly used for desktop and larger peripheral equipment. The Mini-USB connectors (Mini-A, Mini-B, Mini-AB) were introduced for mobile devices. Still, they were quickly replaced by the thinner Micro-USB connectors (Micro-A, Micro-B, Micro-AB). The Type-C connector, also known as USB-C, is not exclusive to USB, is the only current standard for USB, is required for USB4, and is required by other standards, including modern DisplayPort and Thunderbolt. It is reversible and can support various functionalities and protocols, including USB; some are mandatory, and many are optional, depending on the type of hardware: host, peripheral device, or hub.[10][11]

High-speed USB 2.0 hubs contain devices called transaction translators that convert between high-speed USB 2.0 buses and full and low speed buses. There may be one translator per hub or per port.

The SuperSpeed architecture provides for an operation mode at a rate of 5.0 Gbit/s, in addition to the three existing operation modes. Its efficiency is dependent on a number of factors including physical symbol encoding and link-level overhead. At a 5 Gbit/s signaling rate with 8b/10b encoding, each byte needs 10 bits to transmit, so the raw throughput is 500 MB/s. When flow control, packet framing and protocol overhead are considered, it is realistic for about two thirds of the raw throughput, or 330 MB/s to transmit to an application.[30]: 4–19  SuperSpeed's architecture is full-duplex; all earlier implementations, USB 1.0-2.0, are all half-duplex, arbitrated by the host.[31]

Universal Serial Bus (USB) is an industry standard that allows data exchange and delivery of power between many types of electronics. It specifies its architecture, in particular its physical interface, and communication protocols for data transfer and power delivery to and from hosts, such as personal computers, to and from peripheral devices, e.g. displays, keyboards, and mass storage devices, and to and from intermediate hubs, which multiply the number of a host's ports.[2]

USB 3.0 adds a new architecture and protocol named SuperSpeed, with associated backward-compatible plugs, receptacles, and cables. SuperSpeed plugs and receptacles are identified with a distinct logo and blue inserts in standard format receptacles.

USB 2.0 was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (maximum theoretical data throughput 53 MByte/s[25]) named High Speed or High Bandwidth, in addition to the USB 1.x Full Speed signaling rate of 12 Mbit/s (maximum theoretical data throughput 1.2 MByte/s).[26]

The USB 3.1 specification introduced an Enhanced SuperSpeed System – while preserving the SuperSpeed architecture and protocol (SuperSpeed USB) – with an additional SuperSpeedPlus architecture and protocol (aka SuperSpeedPlus USB) adding a new coding schema (128b/132b symbols, 10 Gbit/s; also known as Gen 2); for some time marketed as SuperSpeed+ (SS+).

The USB-IF used WiGig Serial Extension v1.2 specification as its initial foundation for the MA-USB specification and is compliant with SuperSpeed USB (3.0 and 3.1) and Hi-Speed USB (USB 2.0). Devices that use MA-USB will be branded as "Powered by MA-USB", provided the product qualifies its certification program.[104]

See more Selenium products. Selenium (atomic symbol: Se, atomic number: 34) is a Block P, Group 16, Period 4 element with an atomic radius of 78.96. The number of electrons in each of Selenium's shells is 2, 8, 18, 6 and its electron configuration is [Ar] 3d10 4s2 4p4. The selenium atom has a radius of 120 pm and a Van der Waals radius of 190 pm. Selenium is a non-metal with several allotropes: a black, vitreous form with an irregular crystal structure three red-colored forms with monoclinic crystal structures and a gray form with a hexagonal crystal structure, the most stable and dense form of the element. One of the most common uses for selenium is in glass production the red tint that it lends to glass neutralizes green or yellow tints from impurities in the glass materials. Selenium was discovered and first isolated by Jöns Jakob Berzelius and Johann Gottlieb Gahn in 1817. The origin of the name Selenium comes from the Greek word "Selênê," meaning moon.

Waste treatment methodsRecommendationConsult official regulations to ensure proper disposal.Uncleaned packagings:Recommendation:Disposal must be made according to official regulations.

Because there are two separate controllers in each USB 3.0 host, USB 3.0 devices transmit and receive at USB 3.0 signaling rates regardless of USB 2.0 or earlier devices connected to that host. Operating signaling rates for earlier devices are set in the legacy manner.

These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum signaling rate, FireWire 400 is faster than USB 2.0 high-bandwidth in real-use,[107] especially in high-bandwidth use such as external hard drives.[108][109][110][111] The newer FireWire 800 standard is twice as fast as FireWire 400 and faster than USB 2.0 high-bandwidth both theoretically and practically.[112] However, FireWire's speed advantages rely on low-level techniques such as direct memory access (DMA), which in turn have created opportunities for security exploits such as the DMA attack.

Information on basic physical and chemical propertiesAppearance:Form: Solid in various formsColor: RedOdor: OdorlessOdor threshold: No data available.pH: N/AMelting point/Melting range: >1100 °C (>2012 °F)Boiling point/Boiling range: No data availableSublimation temperature / start: No data availableFlash point: N/AFlammability (solid, gas): No data available.Ignition temperature: No data availableDecomposition temperature: No data availableAutoignition: No data available.Danger of explosion: Product does not present an explosion hazard.Explosion limits:Lower: No data availableUpper: No data availableVapor pressure: N/ADensity at 20 °C (68 °F): 5.42 g/cm3 (45.23 lbs/gal)Relative density: No data available.Vapor density: N/AEvaporation rate: N/ASolubility in Water (H2O): InsolublePartition coefficient (n-octanol/water): No data available.Viscosity:Dynamic: N/AKinematic: N/AOther informationNo data available

USB-C (officially USB Type-C) is a standard that defines a new connector, and several new connection features. Among them it supports Alternate Mode, which allows transporting other protocols via the USB-C connector and cable. This is commonly used to support the DisplayPort or HDMI protocols, which allows connecting a display, such as a computer monitor or television set, via USB-C.

SubstancesCAS No. / Substance Name:1315-09-9 Zinc selenideIdentification number(s):EC number: 215-259-7Index number: 034-002-00-8

A USB connection is always between an A end, either a host or a downstream port of a hub, and a B end, either a peripheral device or the upstream port of a hub. Historically this was made clear by the fact that hosts had only Type-A ports and peripheral devices had only Type-B, and every (valid) cable had one Type-A plug and one Type-B plug. USB-C (Type-C) is a single connector that replaces all Type-A and Type-B connectors (legacy connectors), so when both sides are modern equipment with USB-C ports they negotiate which is the host (A) and which is the device (B).

The USB 3.0 specification was released on 12 November 2008, with its management transferring from USB 3.0 Promoter Group to the USB Implementers Forum (USB-IF) and announced on 17 November 2008 at the SuperSpeed USB Developers Conference.[29]

The design is intended to make it difficult to insert a USB plug into its receptacle incorrectly. The USB specification requires that the cable plug and receptacle be marked so the user can recognize the proper orientation.[30] The USB-C plug however is reversible. USB cables and small USB devices are held in place by the gripping force from the receptacle, with no screws, clips, or thumb-turns as some connectors use.

A USB system consists of a host with one or more downstream facing ports (DFP),[57] and multiple peripherals, forming a tiered-star topology. Additional USB hubs may be included, allowing up to five tiers. A USB host may have multiple controllers, each with one or more ports. Up to 127 devices may be connected to a single host controller.[58][30]: 8–29  USB devices are linked in series through hubs. The hub built into the host controller is called the root hub.

USB bridge cables, or data transfer cables can be found within the market, offering direct PC to PC connections. A bridge cable is a special cable with a chip and active electronics in the middle of the cable. The chip in the middle of the cable acts as a peripheral to both computers and allows for peer-to-peer communication between the computers. The USB bridge cables are used to transfer files between two computers via their USB ports.

In versions of Microsoft Windows before Windows XP, Windows would automatically run a script (if present) on certain devices via AutoRun, one of which are USB mass storage devices, which may contain malicious software.[125]

Ultraviolet/ultrasound-activated persulfate for degradation of drug by zinc selenide quantum dots: Catalysis and microbiology study.

Popularized by Microsoft as Windows Easy Transfer, the Microsoft utility used a special USB bridge cable to transfer personal files and settings from a computer running an earlier version of Windows to a computer running a newer version. In the context of the use of Windows Easy Transfer software, the bridge cable can sometimes be referenced as Easy Transfer cable.

Safety Data Sheet according to Regulation (EC) No. 1907/2006 (REACH). The above information is believed to be correct but does not purport to be all inclusive and shall be used only as a guide. The information in this document is based on the present state of our knowledge and is applicable to the product with regard to appropriate safety precautions. It does not represent any guarantee of the properties of the product. American Elements shall not be held liable for any damage resulting from handling or from contact with the above product. See reverse side of invoice or packing slip for additional terms and conditions of sale. COPYRIGHT 1997-2022 AMERICAN ELEMENTS. LICENSED GRANTED TO MAKE UNLIMITED PAPER COPIES FOR INTERNAL USE ONLY.

As of 2024,[update] USB consists of four generations of specifications: USB 1.x, USB 2.0, USB 3.x, and USB4. USB4 enhances the data transfer and power delivery functionality with

USB connector interfaces are classified into three types: the many various legacy Type-A (upstream) and Type-B (downstream) connectors found on hosts, hubs, and peripheral devices, and the modern Type-C (USB-C) connector, which replaces the many legacy connectors as the only applicable connector for USB4.

eSATA does not supply power to external devices. This is an increasing disadvantage compared to USB. Even though USB 3.0's 4.5 W is sometimes insufficient to power external hard drives, technology is advancing, and external drives gradually need less power, diminishing the eSATA advantage. eSATAp (power over eSATA, a.k.a. ESATA/USB) is a connector introduced in 2009 that supplies power to attached devices using a new, backward compatible, connector. On a notebook eSATAp usually supplies only 5 V to power a 2.5-inch HDD/SSD; on a desktop workstation it can additionally supply 12 V to power larger devices including 3.5-inch HDD/SSD and 5.25-inch optical drives.

UAC 2.0 introduced support for High Speed USB (in addition to Full Speed), allowing greater bandwidth for multi-channel interfaces, higher sample rates,[75] lower inherent latency,[76][72] and 8× improvement in timing resolution in synchronous and adaptive modes.[72] UAC2 also introduced the concept of clock domains, which provides information to the host about which input and output terminals derive their clocks from the same source, as well as improved support for audio encodings like DSD, audio effects, channel clustering, user controls, and device descriptions.[72][77]

Safety, health and environmental regulations/legislation specific for the substance or mixtureNational regulationsAll components of this product are listed in the U.S. Environmental Protection Agency Toxic Substances Control Act Chemical substance Inventory.All components of this product are listed on the Canadian Non-Domestic Substances List (NDSL).SARA Section 313 (specific toxic chemical listings)1315-09-9 Zinc selenideCalifornia Proposition 65Prop 65 - Chemicals known to cause cancerSubstance is not listed.Prop 65 - Developmental toxicitySubstance is not listed.Prop 65 - Developmental toxicity, femaleSubstance is not listed.Prop 65 - Developmental toxicity, maleSubstance is not listed.Information about limitation of use:For use only by technically qualified individuals.This product contains selenium and is subject to the reporting requirements of section 313 of the Emergency Planning and Community Right to Know Act of 1986 and 40CFR372.This product contains zinc and is subject to the reporting requirements of section 313 of the Emergency Planning and CommunityRight to Know Act of 1986 and40CFR372.Other regulations, limitations and prohibitive regulationsSubstance of Very High Concern (SVHC) according to the REACH Regulations (EC) No. 1907/2006.Substance is not listed.The conditions of restrictions according to Article 67 and Annex XVII of the Regulation (EC) No 1907/2006 (REACH) for the manufacturing, placing on the market and use must be observed.Substance is not listed.Annex XIV of the REACH Regulations (requiring Authorisation for use)Substance is not listed.Chemical safety assessment:A Chemical Safety Assessment has not been carried out.

The eSATA connector is a more robust SATA connector, intended for connection to external hard drives and SSDs. eSATA's transfer rate (up to 6 Gbit/s) is similar to that of USB 3.0 (up to 5 Gbit/s) and USB 3.1 (up to 10 Gbit/s). A device connected by eSATA appears as an ordinary SATA device, giving both full performance and full compatibility associated with internal drives.

In 2023, they were replaced again,[39] removing "SuperSpeed", with USB 5Gbps, USB 10Gbps, and USB 20Gbps. With new Packaging and Port logos.[40]

The USB Device Working Group has laid out specifications for audio streaming, and specific standards have been developed and implemented for audio class uses, such as microphones, speakers, headsets, telephones, musical instruments, etc. The working group has published three versions of audio device specifications:[70][71] USB Audio 1.0, 2.0, and 3.0, referred to as "UAC"[72] or "ADC".[73]

Another use for USB mass storage devices is the portable execution of software applications (such as web browsers and VoIP clients) with no need to install them on the host computer.[64][65]

Several manufacturers offer external portable USB hard disk drives, or empty enclosures for disk drives. These offer performance comparable to internal drives, limited by the number and types of attached USB devices, and by the upper limit of the USB interface. Other competing standards for external drive connectivity include eSATA, ExpressCard, FireWire (IEEE 1394), and most recently Thunderbolt.

Thunderbolt combines PCI Express and Mini DisplayPort into a new serial data interface. Original Thunderbolt implementations have two channels, each with a transfer speed of 10 Gbit/s, resulting in an aggregate unidirectional bandwidth of 20 Gbit/s.[118]

In addition to standard USB, there is a proprietary high-powered system known as PoweredUSB, developed in the 1990s, and mainly used in point-of-sale terminals such as cash registers.

Device Firmware Upgrade (DFU) is a generic mechanism for upgrading the firmware of USB devices with improved versions provided by their manufacturers, offering (for example) a way to deploy firmware bug fixes. During the firmware upgrade operation, USB devices change their operating mode effectively becoming a PROM programmer. Any class of USB device can implement this capability by following the official DFU specifications. Doing so allows use of DFU-compatible host tools to update the device.[63][67][68]

Endpoints are grouped into interfaces and each interface is associated with a single device function. An exception to this is endpoint zero, which is used for device configuration and is not associated with any interface. A single device function composed of independently controlled interfaces is called a composite device. A composite device only has a single device address because the host only assigns a device address to a function.

Additional information about design of technical systems:Properly operating chemical fume hood designed for hazardous chemicals and having an average face velocity of at least 100 feet per minute.Control parametersComponents with limit values that require monitoring at the workplace:Selenium and selenium compounds (as Se) mg/m3ACGIH TLV 0.2Austria MAK 0.1Belgium TWA 0.2Denmark TWA 0.1Finland TWA 0.1; 0.3-STELGermany MAK 0.1Hungary 0.1-STELIreland TLV 0.1Japan OEL 0.1Korea TLV 0.2Netherlands MAC-TGG 0.1Poland TWA 0.1; 0.3-STELSweden NGV 0.1Switzerland MAK-W 0.1United Kingdom TWA 0.1USA PEL 0.21315-09-9 Zinc selenide (100.0%)PEL (USA) Long-term value: 0.2 mg/m3 as SeREL (USA) Long-term value: 0.2 mg/m3 as SeTLV (USA) Long-term value: 0.2 mg/m3 as SeEL (Canada) Long-term value: 0.1 mg/m3 as SeAdditional information: No dataExposure controlsPersonal protective equipmentFollow typical protective and hygienic practices for handling chemicals.Keep away from foodstuffs, beverages and feed.Remove all soiled and contaminated clothing immediately.Wash hands before breaks and at the end of work.Store protective clothing separately.Maintain an ergonomically appropriate working environment.Breathing equipment:Use self-contained respiratory protective device in emergency situations.Protection of hands: Impervious glovesInspect gloves prior to use.Suitability of gloves should be determined both by material and quality, the latter of which may vary by manufacturer.Eye protection: Safety glassesBody protection: Protective work clothing.

The functionality of a USB device is defined by a class code sent to a USB host. This allows the host to load software modules for the device and to support new devices from different manufacturers.

Information on toxicological effectsAcute toxicity:Toxic if inhaled.Toxic if swallowed.LD/LC50 values that are relevant for classification: No dataSkin irritation or corrosion: May cause irritationEye irritation or corrosion: May cause irritationSensitization: No sensitizing effects known.Germ cell mutagenicity: No effects known.Carcinogenicity:No classification data on carcinogenic properties of this material is available from the EPA, IARC, NTP, OSHA or ACGIH.Reproductive toxicity: No effects known.Specific target organ system toxicity - repeated exposure:May cause damage to the central nervous system, the liver and the digestive system through prolonged or repeated exposure. Route of exposure: Oral, Inhalative.Specific target organ system toxicity - single exposure: No effects known.Aspiration hazard: No effects known.Subacute to chronic toxicity:Selenium may cause amyotropic lateral sclerosis, bronchial irritation, gastrointestinal distress, vasopharyngeal irritation, garlic odor on breath and sweat, metallic taste, pallor, irritability, excessive fatigue, loss of fingernails and hair, pulmonary edema, anemia and weight loss.Zinc fumes may cause metal fume fever. Effects include dry throat, metallic taste, chest pain, dyspnea, rales and dry cough.Several hours later, chills may occur with lassitude, malaise, fatigue, headache, back pain, muscle cramps, blurred vision, nausea, fever, perspiration, vomiting and leukocytosis.Subacute to chronic toxicity: No effects known.Additional toxicological information:To the best of our knowledge the acute and chronic toxicity of this substance is not fully known.Carcinogenic categoriesOSHA-Ca (Occupational Safety & Health Administration)Substance is not listed.

Introduced in 1996, USB was originally designed to standardize the connection of peripherals to computers, replacing various interfaces such as serial ports, parallel ports, game ports, and ADB ports.[3] Early versions of USB became commonplace on a wide range of devices, such as keyboards, mice, cameras, printers, scanners, flash drives, smartphones, game consoles, and power banks.[4] USB has since evolved into a standard to replace virtually all common ports on computers, mobile devices, peripherals, power supplies, and manifold other small electronics.

Product Number: All applicable American Elements product codes, e.g. ZN-SE-02-LNSP , ZN-SE-03-LNSP , ZN-SE-04-LNSP , ZN-SE-05-LNSP

The IEEE 802.3af, 802.3at, and 802.3bt Power over Ethernet (PoE) standards specify more elaborate power negotiation schemes than powered USB. They operate at 48 V DC and can supply more power (up to 12.95 W for 802.3af, 25.5 W for 802.3at, a.k.a. PoE+, 71 W for 802.3bt, a.k.a. 4PPoE) over a cable up to 100 meters compared to USB 2.0, which provides 2.5 W with a maximum cable length of 5 meters. This has made PoE popular for Voice over IP telephones, security cameras, wireless access points, and other networked devices within buildings. However, USB is cheaper than PoE provided that the distance is short and power demand is low.

USB specifications provide backward compatibility, usually resulting in decreased signaling rates, maximal power offered, and other capabilities. The USB 1.1 specification replaces USB 1.0. The USB 2.0 specification is backward-compatible with USB 1.0/1.1. The USB 3.2 specification replaces USB 3.1 (and USB 3.0) while including the USB 2.0 specification. USB4 "functionally replaces" USB 3.2 while retaining the USB 2.0 bus operating in parallel.[5][6][7][2]

Due to the prevalency of the USB standard, there are many exploits using the USB standard. One of the biggest instances of this today is known as the USB killer, a device that damages USB devices by sending high voltage pulses across the data lines.

UAC 1.0 devices are still common, however, due to their cross-platform driverless compatibility,[75] and also partly due to Microsoft's failure to implement UAC 2.0 for over a decade after its publication, having finally added support to Windows 10 through the Creators Update on 20 March 2017.[78][79][77] UAC 2.0 is also supported by macOS, iOS, and Linux,[72] however Android only implements a subset of the UAC 1.0 specification.[80]

Devices that draw no more than one unit are said to be low-power devices. All devices must act as low-power devices when starting out as unconfigured. For USB devices up to USB 2.0 a unit load is 100 mA (or 500 mW), while USB 3.0 defines a unit load as 150 mA (750 mW). Full-featured USB-C can support low-power devices with a unit load of 250 mA (or 1250 mW).

All other connectors are not capable of two-lane operations (Gen 1×2 and Gen 2×2) in USB 3.2, but can be used for one-lane operations (Gen 1×1 and Gen 2×1).[106]

The operation modes USB 3.2 Gen 2×2 and USB4 Gen 2×2 – or: USB 3.2 Gen 2×1 and USB4 Gen 2×1 – are not interchangeable or compatible; all participating controllers must operate with the same mode.

The USB 3.0 specification defined a new architecture and protocol named SuperSpeed (aka SuperSpeed USB, marketed as SS), which included a new lane for a new signal coding scheme (8b/10b symbols, 5 Gbit/s; later also known as Gen 1) providing full-duplex data transfers that physically required five additional wires and pins, while preserving the USB 2.0 architecture and protocols and therefore keeping the original four pins/wires for the USB 2.0 backward-compatibility resulting in 9 wires (with 9 or 10 pins at connector interfaces; ID-pin is not wired) in total.

USB is competitive for low-cost and physically adjacent devices. However, Power over Ethernet and the MIDI plug standard have an advantage in high-end devices that may have long cables. USB can cause ground loop problems between equipment, because it connects ground references on both transceivers. By contrast, the MIDI plug standard and Ethernet have built-in isolation to 500V or more.

The Study of Metal Sulfide as Efficient Counter Electrodes on the Performances of CdS/CdSe/ZnS-co-sensitized Hierarchical TiO2 Sphere Quantum Dot Solar Cells.

The chipset and drivers used to implement USB and FireWire have a crucial impact on how much of the bandwidth prescribed by the specification is achieved in the real world, along with compatibility with peripherals.[113]

During CES 2020, USB-IF and Intel stated their intention to allow USB4 products that support all the optional functionality as Thunderbolt 4 products.

See more Zinc products. Zinc (atomic symbol: Zn, atomic number: 30) is a Block D, Group 12, Period 4 element with an atomic weight of 65.38. The number of electrons in each of zinc's shells is 2, 8, 18, 2, and its electron configuration is [Ar] 3d10 4s2. The zinc atom has a radius of 134 pm and a Van der Waals radius of 210 pm. Zinc was discovered by Indian metallurgists prior to 1000 BC and first recognized as a unique element by Rasaratna Samuccaya in 800. Zinc was first isolated by Andreas Marggraf in 1746. In its elemental form, zinc has a silver-gray appearance. It is brittle at ordinary temperatures but malleable at 100 °C to 150 °C. It is a fair conductor of electricity, and burns in air at high red producing white clouds of the oxide. Zinc is mined from sulfidic ore deposits. It is the 24th most abundant element in the earth's crust and the fourth most common metal in use (after iron, aluminum, and copper). The name zinc originates from the German word "zin," meaning tin.

Starting with the USB 3.2 specification, USB-IF introduced a new naming scheme.[37] To help companies with the branding of the different operation modes, USB-IF recommended branding the 5, 10, and 20 Gbit/s capabilities as SuperSpeed USB 5Gbps, SuperSpeed USB 10 Gbps, and SuperSpeed USB 20 Gbps, respectively.[38]

DisplayPort Alternate Mode 2.0: USB4 (requiring USB-C) requires that hubs support DisplayPort 2.0 over a USB-C Alternate Mode. DisplayPort 2.0 can support 8K resolution at 60 Hz with HDR10 color.[123] DisplayPort 2.0 can use up to 80 Gbit/s, which is double the amount available to USB data, because it sends all the data in one direction (to the monitor) and can thus use all eight data wires at once.[123]

Ethernet standards require electrical isolation between the networked device (computer, phone, etc.) and the network cable up to 1500 V AC or 2250 V DC for 60 seconds.[114] USB has no such requirement as it was designed for peripherals closely associated with a host computer, and in fact it connects the peripheral and host grounds. This gives Ethernet a significant safety advantage over USB with peripherals such as cable and DSL modems connected to external wiring that can assume hazardous voltages under certain fault conditions.[115][116]

USB signals are transmitted using differential signaling on twisted-pair data wires with 90 Ω ± 15% characteristic impedance.[98] USB 2.0 and earlier specifications define a single pair in half-duplex (HDx). USB 3.0 and later specifications define one dedicated pair for USB 2.0 compatibility and two or four pairs for data transfer: two pairs in full-duplex (FDx) for single lane variants require at least SuperSpeed (SS) connectors; four pairs in full-duplex for two lane (×2) variants require USB-C connectors. USB4 Gen 4 requires the use of all four pairs but allow for asymmetrical pairs configuration.[99] In this case one lane is used for the upstream data and the other three for the downstream data or vice-versa. USB4 Gen 4 use pulse amplitude modulation on 3 levels, providing a trit of information every baud transmitted, the transmission frequency of 12.8 GHz translate to a transmission rate of 25.6 GBd[100] and the 11-bit–to–7-trit translation provides a theoretical maximum transmission speed just over 40.2 Gbit/s.[101]

The USB mass storage device class (MSC or UMS) standardizes connections to storage devices. At first intended for magnetic and optical drives, it has been extended to support flash drives and SD card readers. The ability to boot a write-locked SD card with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium.

To recognize Battery Charging mode, a dedicated charging port places a resistance not exceeding 200 Ω across the D+ and D− terminals. Shorted or near-shorted data lanes with less than 200 Ω of resistance across the D+ and D− terminals signify a dedicated charging port (DCP) with indefinite charging rates.[96][97]

UN-NumberDOT, IMDG, IATAUN3283UN proper shipping nameDOTSelenium compound, solid, n.o.s. (Zinc selenide)IMDGSELENIUM COMPOUND, SOLID, N.O.S.(Zinc selenide), MARINE POLLUTANTIATASELENIUM COMPOUND, SOLID, N.O.S. (Zinc selenide)Transport hazard class(es)DOTClass6.1 Toxic substances.Label6.1Class6.1 (T5) Toxic substancesLabel6.1IMDGClass6.1 Toxic substances.Label6.1IATAClass6.1 Toxic substances.Label6.1Packing groupDOT, IMDG, IATAIIIEnvironmental hazards:Environmentally hazardous substance, solid; Marine PollutantMarine pollutant (IMDG):Yes (P)Symbol (fish and tree)Special precautions for userWarning: Toxic substancesEMS Number:F-A,S-ATransport in bulk according to Annex II of MARPOL73/78 and the IBC CodeN/ATransport/Additional information:DOTMarine Pollutant (DOT):NoRemarks:Special marking with the symbol (fish and tree).UN "Model Regulation":UN3283, Selenium compound, solid, n.o.s. (Zinc selenide), 6.1, III

USB device communication is based on pipes (logical channels). A pipe connects the host controller to a logical entity within a device, called an endpoint. Because pipes correspond to endpoints, the terms are sometimes used interchangeably. Each USB device can have up to 32 endpoints (16 in and 16 out), though it is rare to have so many. Endpoints are defined and numbered by the device during initialization (the period after physical connection called "enumeration") and so are relatively permanent, whereas pipes may be opened and closed.

The USB Implementers Forum introduced the Media Agnostic USB (MA-USB) v.1.0 wireless communication standard based on the USB protocol on 29 July 2015. Wireless USB is a cable-replacement technology, and uses ultra-wideband wireless technology for data rates of up to 480 Mbit/s.[103]

USB 3.2, released in September 2017,[35] preserves existing USB 3.1 SuperSpeed and SuperSpeedPlus architectures and protocols and their respective operation modes, but introduces two additional SuperSpeedPlus operation modes (USB 3.2 Gen 1×2 and USB 3.2 Gen 2×2) with the new USB-C Fabric with signaling rates of 10 and 20 Gbit/s (raw data rates of 1212 and 2424 MB/s). The increase in bandwidth is a result of two-lane operation over existing wires that were originally intended for flip-flop capabilities of the USB-C connector.[36]

Because of the previous confusing naming schemes, USB-IF decided to change it once again. As of 2 September 2022, marketing names follow the syntax "USB xGbps", where x is the speed of transfer in Gbit/s.[49] Overview of the updated names and logos can be seen in the adjacent table.

For a product developer, using USB requires the implementation of a complex protocol and implies an "intelligent" controller in the peripheral device. Developers of USB devices intended for public sale generally must obtain a USB ID, which requires that they pay a fee to the USB Implementers Forum (USB-IF). Developers of products that use the USB specification must sign an agreement with the USB-IF. Use of the USB logos on the product requires annual fees and membership in the organization.[12]

Modeling and optimization of ultrasound-assisted high performance adsorption of Basic Fuchsin by starch-capped zinc selenide nanoparticles/AC as a novel composite using response surface methodology.

Thunderbolt 3 and Thunderbolt 4 use USB-C.[120][121][122] Thunderbolt 3 has two physical 20 Gbit/s bi-directional channels, aggregated to appear as a single logical 40 Gbit/s bi-directional channel. Thunderbolt 3 controllers can incorporate a USB 3.1 Gen 2 controller to provide compatibility with USB devices. They are also capable of providing DisplayPort Alternate Mode as well as DisplayPort over USB4 Fabric, making the function of a Thunderbolt 3 port a superset of that of a USB 3.1 Gen 2 port.

Many USB bridge / data transfer cables are still USB 2.0, but there are also a number of USB 3.0 transfer cables. Despite USB 3.0 being 10 times faster than USB 2.0, USB 3.0 transfer cables are only 2 to 3 times faster given their design.[clarification needed]

Neither USB 1.0 nor 1.1 specified a design for any connector smaller than the standard type A or type B. Though many designs for a miniaturized type B connector appeared on many peripherals, conformity to the USB 1.x standard was hampered by treating peripherals that had miniature connectors as though they had a tethered connection (that is: no plug or receptacle at the peripheral end). There was no known miniature type A connector until USB 2.0 (revision 1.01) introduced one.

Personal precautions, protective equipment and emergency proceduresUse personal protective equipment. Keep unprotected persons away.Ensure adequate ventilationEnvironmental precautions:Do not allow material to be released to the environment without official permits.Methods and materials for containment and cleanup:Dispose of contaminated material as waste according to section 13.Ensure adequate ventilation.Prevention of secondary hazards:No special measures required.Reference to other sectionsSee Section 7 for information on safe handlingSee Section 8 for information on personal protection equipment.See Section 13 for disposal information.

Influence of Post-Heat Treatment of ZnO:Al Transparent Electrode for Copper Indium Gallium Selenide Thin Film Solar Cell.

Each specification sub-version supports different signaling rates from 1.5 and 12 Mbit/s total in USB 1.0 to 80 Gbit/s (in each direction) in USB4.[5][6][7][2] USB also provides power to peripheral devices; the latest versions of the standard extend the power delivery limits for battery charging and devices requiring up to 240 watts (USB Power Delivery (USB-PD)).[8] Over the years, USB(-PD) has been adopted as the standard power supply and charging format for many mobile devices, such as mobile phones, reducing the need for proprietary chargers.[9]

The connectors the USB committee specifies support a number of USB's underlying goals, and reflect lessons learned from the many connectors the computer industry has used. The female connector mounted on the host or device is called the receptacle, and the male connector attached to the cable is called the plug.[30]: 2-5–2-6  The official USB specification documents also periodically define the term male to represent the plug, and female to represent the receptacle.[90]

USB 3.0 also introduced the USB Attached SCSI protocol (UASP), which provides generally faster transfer speeds than the BOT (Bulk-Only-Transfer) protocol.

Though most personal computers since early 2005 can boot from USB mass storage devices, USB is not intended as a primary bus for a computer's internal storage. However, USB has the advantage of allowing hot-swapping, making it useful for mobile peripherals, including drives of various kinds.

DFU is sometimes used as a flash memory programming protocol in microcontrollers with built-in USB bootloader functionality. [69]

USB was designed to standardize the connection of peripherals to personal computers, both to exchange data and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports and has become commonplace on various devices. Peripherals connected via USB include computer keyboards and mice, video cameras, printers, portable media players, mobile (portable) digital telephones, disk drives, and network adapters.

A USB mouse or keyboard can usually be used with older computers that have PS/2 ports with the aid of a small USB-to-PS/2 adapter. For mice and keyboards with dual-protocol support, a passive adapter that contains no logic circuitry may be used: the USB hardware in the keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol.[citation needed] Active converters that connect USB keyboards and mice (usually one of each) to PS/2 ports also exist.[66]

During USB communication, data is transmitted as packets. Initially, all packets are sent from the host via the root hub, and possibly more hubs, to devices. Some of those packets direct a device to send some packets in reply.

At first, USB was considered a complement to FireWire (IEEE 1394) technology, which was designed as a high-bandwidth serial bus that efficiently interconnects peripherals such as disk drives, audio interfaces, and video equipment. In the initial design, USB operated at a far lower data rate and used less sophisticated hardware. It was suitable for small peripherals such as keyboards and pointing devices.