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104-616: The initial versions of the USB standard specified connectors that were easy to use and that would have acceptable life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data paths. All versions of USB specify cable properties; version 3. x cables include additional data paths. The USB standard included power supply to peripheral devices; modern versions of

208-421: A unit load which is 100 mA for USB 2.0, or 150 mA for SuperSpeed (i.e. USB 3. x ) devices. Low-power devices may draw at most 1 unit load, and all devices must act as low-power devices before they are configured. A high-powered device must be configured, after which it may draw up to 5 unit loads (500 mA), or 6 unit loads (900 mA) for SuperSpeed devices, as specified in its configuration because

312-455: A B plug, that plug determining the behavior of the receptacle. The three sizes of USB connectors are the default, or standard , format intended for desktop or portable equipment, the mini intended for mobile equipment, which was deprecated when it was replaced by the thinner micro size, all of which were deprecated in USB 3.2 in favor of Type-C. There are five speeds for USB data transfer: Low Speed, Full Speed, High Speed (from version 2.0 of

416-484: A Micro-AB receptacle. (In the past, before the development of Micro-USB, On-The-Go devices used Mini -AB receptacles.) The Micro-AB receptacle is capable of accepting Micro-A and Micro-B plugs, attached to any of the legal cables and adapters as defined in revision 1.01 of the Micro-USB specification. To enable Type-AB receptacles to distinguish which end of a cable is plugged in, plugs have an "ID" pin in addition to

520-530: A USB standard port. Full functionality of proprietary ports and cables with USB standard ports is not assured; for example, some devices only use the USB connection for battery charging and do not implement any data transfer functions. The D± signals used by low, full, and high speed are carried over a twisted pair (typically unshielded) to reduce noise and crosstalk . SuperSpeed uses separate transmit and receive differential pairs , which additionally require shielding (typically, shielded twisted pair but twinax

624-558: A USB-C receptacle are not allowed. Full-featured USB-C 3.1 cables contain a full set of wires and are "electronically marked" ( E-marked ): they contain a "eMarker" chip that responds to the USB Power Delivery Discover Identity command, a kind of vendor-defined message (VDM) sent over the configuration data channel (CC). Using this command, the cable reports its current capacities, maximum speed, and other parameters. Full-Featured USB Type-C devices are

728-445: A built-in hub that connects to the physical USB cable. 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

832-748: A charge-only cable, the data wires are shorted at the device end, otherwise, the device may reject the charger as unsuitable. The maximum allowed cross-section of the overmold boot (which is part of the connector used for its handling) is 16 by 8 mm (0.63 by 0.31 in) for the Standard-A plug type, while for the Type-B it is 11.5 by 10.5 mm (0.45 by 0.41 in). Mini-USB connectors were introduced together with USB 2.0 in April 2000, mostly used with smaller devices such as digital cameras , smartphones , and tablet computers . The Mini-A connector and

936-411: A cutting or plowing operation. Three-body wear occurs when the particles are not constrained, and are free to roll and slide down a surface. The contact environment determines whether the wear is classified as open or closed. An open contact environment occurs when the surfaces are sufficiently displaced to be independent of one another There are a number of factors which influence abrasive wear and hence

1040-405: A device with two logical B ports, each with a captive cable, not a cable with two A ends. The standard connectors were designed to be more robust than many past connectors. This is because USB is hot-swappable , and the connectors would be used more frequently, and perhaps with less care, than previous connectors. Standard USB has a minimum rated lifetime of 1,500 cycles of insertion and removal,

1144-551: A low-power upstream port). The USB 3. x specifications require that all devices must operate down to 4.00 V at the device port. Unlike USB 2.0 and USB 3.2, USB4 does not define its own VBUS-based power model. Power for USB4 operation is established and managed as defined in the USB Type-C Specification and the USB PD Specification. The limit to device power draw is stated in terms of

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1248-408: A maximum cable length of 5 metres (16 ft 5 in) for devices running at high speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to

1352-563: A mechanic prerequisite for multi-lane operation (USB 3.2 Gen 1x2, USB 3.2 Gen 2x2, USB4 2x2, USB4 3x2, USB Gen 4 Asymmetric). USB-C devices support power currents of 1.5 A and 3.0 A over the 5 V power bus in addition to baseline 900 mA. These higher currents can be negotiated through the configuration line. Devices can also utilize the full Power Delivery specification using both BMC-coded configuration line and legacy BFSK -coded V BUS line. USB plugs fit one receptacle with notable exceptions for USB On-The-Go "AB" support and

1456-682: A new coding schema (128b/132b symbols, 10 Gbit/s; also known as Gen 2 ); for some time marketed as SuperSpeed+ ( SS+ ). The USB 3.2 specification 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

1560-429: A period of time fretting which will remove material from one or both surfaces in contact. It occurs typically in bearings, although most bearings have their surfaces hardened to resist the problem. Another problem occurs when cracks in either surface are created, known as fretting fatigue. It is the more serious of the two phenomena because it can lead to catastrophic failure of the bearing. An associated problem occurs when

1664-426: A solid surface. Abrasive wear is commonly classified according to the type of contact and the contact environment. The type of contact determines the mode of abrasive wear. The two modes of abrasive wear are known as two-body and three-body abrasive wear. Two-body wear occurs when the grits or hard particles remove material from the opposite surface. The common analogy is that of material being removed or displaced by

1768-447: A specific set of test parameter as stipulated in the test description. To obtain more accurate predictions of wear in industrial applications it is necessary to conduct wear testing under conditions simulating the exact wear process. An attrition test is a test that is carried out to measure the resistance of a granular material to wear. The Reye–Archard–Khrushchov wear law is the classic wear prediction model. The wear coefficient

1872-538: A standard to replace virtually all common ports on computers, mobile devices, peripherals, power supplies, and manifold other small electronics. 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. As of 2024, USB consists of four generations of specifications: USB 1. x , USB 2.0 , USB 3. x , and USB4 . USB4 enhances

1976-554: A standard/embedded host have their role fixed by the cable, since in these scenarios it is only possible to attach the cable one way. The USB-C connector supersedes all earlier USB connectors and the Mini DisplayPort connector. It is used for all USB protocols and for Thunderbolt (3 and later), DisplayPort (1.2 and later), and others. Developed at roughly the same time as the USB ;3.1 specification, but distinct from it,

2080-526: 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. 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 ) 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). Modifications to

2184-508: Is full-duplex ; all earlier implementations, USB 1.0-2.0, are all half-duplex, arbitrated by the host. 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. USB 3.0 also introduced the USB Attached SCSI protocol (UASP) , which provides generally faster transfer speeds than

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2288-539: 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. Wear Wear in machine elements , together with other processes such as fatigue and creep , causes functional surfaces to degrade, eventually leading to material failure or loss of functionality. Thus, wear has large economic relevance as first outlined in

2392-402: Is affected by factors such as type of loading (e.g., impact, static, dynamic), type of motion (e.g., sliding , rolling ), temperature , and lubrication , in particular by the process of deposition and wearing out of the boundary lubrication layer. Depending on the tribosystem , different wear types and wear mechanisms can be observed. Types of wear are identified by relative motion ,

2496-410: Is also called tribocorrosion . Impact wear is caused by contact between two bodies. Unlike erosive wear, impact wear always occurs at the same, well-defined place. If the impact is repeated, then usually with constant kinetic energy at the moment of impact. The frequency of impacts can vary. Wear can occur on both bodies, but usually, one body has significantly higher hardness and toughness and its wear

2600-465: Is also mentioned by the specification). Thus, to support SuperSpeed data transmission, cables contain twice as many wires and are larger in diameter. The USB 1.1 standard specifies that a standard cable can have a maximum length of 5 metres (16 ft 5 in) with devices operating at full speed (12 Mbit/s), and a maximum length of 3 metres (9 ft 10 in) with devices operating at low speed (1.5 Mbit/s). USB 2.0 provides for

2704-452: Is implemented in a USB-C cable), four pairs for SuperSpeed data bus (only two pairs are used in USB 3.1 mode), two "sideband use" pins, V CONN +5 V power for active cables, and a configuration pin for cable orientation detection and dedicated biphase mark code (BMC) configuration data channel (CC). Type-A and Type-B adaptors and cables are required for older hosts and devices to plug into USB-C hosts and devices. Adapters and cables with

2808-534: 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. See the USB On-The-Go connectors section below for a more detailed summary description. There are so-called cables with A plugs on both ends, which may be valid if the "cable" includes, for example, a USB host-to-host transfer device with two ports. This is, by definition,

2912-402: Is made using two connectors: a receptacle and a plug . Pictures show only receptacles: 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. From the computer user's perspective,

3016-975: Is neglected. Other, less common types of wear are cavitation and diffusive wear. Under nominal operation conditions, the wear rate normally changes in three different stages: The wear rate is strongly influenced by the operating conditions and the formation of tribofilms . The secondary stage is shortened with increasing severity of environmental conditions, such as high temperatures, strain rates and stresses. So-called wear maps, demonstrating wear rate under different operation condition, are used to determine stable operation points for tribological contacts. Wear maps also show dominating wear modes under different loading conditions. In explicit wear tests simulating industrial conditions between metallic surfaces, there are no clear chronological distinction between different wear-stages due to big overlaps and symbiotic relations between various friction mechanisms. Surface engineering and treatments are used to minimize wear and extend

3120-409: Is separated from the surface in the form of primary debris, or microchips, with little or no material displaced to the sides of the grooves. This mechanism closely resembles conventional machining. Fragmentation occurs when material is separated from a surface by a cutting process and the indenting abrasive causes localized fracture of the wear material. These cracks then freely propagate locally around

3224-422: Is the hardness. Surface fatigue is a process in which the surface of a material is weakened by cyclic loading, which is one type of general material fatigue. Fatigue wear is produced when the wear particles are detached by cyclic crack growth of microcracks on the surface. These microcracks are either superficial cracks or subsurface cracks. Fretting wear is the repeated cyclical rubbing between two surfaces. Over

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3328-448: Is the load, α {\displaystyle \alpha } is the shape factor of an asperity (typically ~ 0.1), β {\displaystyle \beta } is the degrees of wear by an asperity (typically 0.1 to 1.0), K {\displaystyle K} is the wear coefficient, L {\displaystyle L} is the sliding distance, and H v {\displaystyle H_{v}}

3432-459: Is the load, K {\displaystyle K} is the wear coefficient, L {\displaystyle L} is the sliding distance, and H v {\displaystyle H_{v}} is the hardness. Abrasive wear occurs when a hard rough surface slides across a softer surface. ASTM International defines it as the loss of material due to hard particles or hard protuberances that are forced against and move along

3536-450: Is velocity, and n {\displaystyle n} is a velocity exponent. n {\displaystyle n} is typically between 2 - 2.5 for metals and 2.5 - 3 for ceramics. Corrosion and oxidation wear occurs both in lubricated and dry contacts. The fundamental cause are chemical reactions between the worn material and the corroding medium. Wear caused by a synergistic action of tribological stresses and corrosion

3640-565: The Jost Report . Abrasive wear alone has been estimated to cost 1–4% of the gross national product of industrialized nations. Wear of metals occurs by plastic displacement of surface and near-surface material and by detachment of particles that form wear debris . The particle size may vary from millimeters to nanometers . This process may occur by contact with other metals, nonmetallic solids, flowing liquids, solid particles or liquid droplets entrained in flowing gasses. The wear rate

3744-728: The USB-IF elected to increase the upper voltage limit to 5.5 V to combat voltage droop at higher currents. The USB 2.0 specification (and therefore implicitly also the USB 3. x specifications) was also updated to reflect this change at that time. A number of extensions to the USB Specifications have progressively further increased the maximum allowable V_BUS voltage: starting with 6.0 V with USB BC 1.2, to 21.5 V with USB PD 2.0 and 50.9 V with USB PD 3.1, while still maintaining backwards compatibility with USB 2.0 by requiring various forms of handshake before increasing

3848-580: The USB-IF on January 4, 2007, have a similar width to Mini-USB, but approximately half the thickness, enabling their integration into thinner portable devices. The Micro-A connector is 6.85 by 1.8 mm (0.270 by 0.071 in) with a maximum overmold boot size of 11.7 by 8.5 mm (0.46 by 0.33 in), while the Micro-B connector is 6.85 by 1.8 mm (0.270 by 0.071 in) with a maximum overmold size of 10.6 by 8.5 mm (0.42 by 0.33 in). The thinner Micro-USB connectors were intended to replace

3952-495: The 5, 10, and 20 Gbit/s capabilities as SuperSpeed USB 5Gbps , SuperSpeed USB 10 Gbps , and SuperSpeed USB 20 Gbps , respectively. In 2023, they were replaced again, removing "SuperSpeed" , with USB 5Gbps , USB 10Gbps , and USB 20Gbps . With new Packaging and Port logos. The USB4 specification was released on 29 August 2019 by the USB Implementers Forum. The USB4 2.0 specification

4056-545: The BOT (Bulk-Only-Transfer) protocol. 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 , 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

4160-691: The Common EPS MoU—for its iPhones equipped with Apple's proprietary 30-pin dock connector or (later) Lightning connector . according to the CEN , CENELEC , and ETSI . USB 3.0 introduced Type-A SuperSpeed plugs and receptacles as well as micro-sized Type-B SuperSpeed plugs and receptacles. The 3.0 receptacles are backward-compatible with the corresponding pre-3.0 plugs. USB 3. x and USB 1. x Type-A plugs and receptacles are designed to interoperate. To achieve USB 3.0's SuperSpeed (and SuperSpeed+ for USB 3.1 Gen 2), 5 extra pins are added to

4264-573: The Mini connectors in devices manufactured since May 2007, including smartphones , personal digital assistants , and cameras. The Micro plug design is rated for at least 10,000 connect-disconnect cycles, which is more than the Mini plug design. The Micro connector is also designed to reduce the mechanical wear on the device; instead, the easier-to-replace cable is designed to bear the mechanical wear of connection and disconnection. The Universal Serial Bus Micro-USB Cables and Connectors Specification details

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4368-560: The Mini-AB receptacle connector have been deprecated since May 2007. Mini-B connectors are still supported, but are not On-The-Go -compliant; the Mini-B USB connector was standard for transferring data to and from the early smartphones and PDAs. Both Mini-A and Mini-B plugs are approximately 3 by 7 mm (0.12 by 0.28 in). The Mini-AB receptacle accepts either a Mini-A or Mini-B plug. Micro-USB connectors, which were announced by

4472-468: The Mini-USB receptacle increased this to 5,000 cycles, and the newer Micro-USB and USB-C receptacles are both designed for a minimum rated lifetime of 10,000 cycles of insertion and removal. To accomplish this, a locking device was added and the leaf-spring was moved from the jack to the plug, so that the most-stressed part is on the cable side of the connection. This change was made so that the connector on

4576-463: The On-The-Go host/client identification. USB 3.0 provides two additional differential pairs (four wires, SSTx+, SSTx−, SSRx+ and SSRx−), providing full-duplex data transfers at SuperSpeed , which makes it similar to Serial ATA or single-lane PCI Express . USB ports and connectors are often color-coded to distinguish their different functions and USB versions. These colors are not part of

4680-501: The SuperSpeed USB Developers Conference. 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. The SuperSpeed architecture provides for an operation mode at a rate of 5.0 Gbit/s, in addition to

4784-405: The USB 2.0 bus operating in parallel. 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

4888-421: 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 connector mounted on the host or device is called the receptacle , and the connector attached to the cable is called the plug . The official USB specification documents also periodically define the term male to represent the plug, and female to represent

4992-416: The USB interface improves ease of use in several ways: The USB standard also provides multiple benefits for hardware manufacturers and software developers, specifically in the relative ease of implementation: As with all standards, USB possesses multiple limitations to its design: For a product developer, using USB requires the implementation of a complex protocol and implies an "intelligent" controller in

5096-493: The USB specification and can vary between manufacturers; for example, the USB 3.0 specification mandates appropriate color-coding while it only recommends blue inserts for Standard-A USB 3.0 connectors and plugs. 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

5200-401: 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: 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

5304-547: 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. 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

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5408-537: The USB-C Specification 1.0 was finalized in August 2014 and defines a new small reversible-plug connector for USB devices. The USB-C plug connects to both hosts and devices, replacing various Type-A and Type-B connectors and cables with a standard meant to be future-proof . The 24-pin double-sided connector provides four power–ground pairs, two differential pairs for USB 2.0 data (though only one pair

5512-531: The components working life. Several standard test methods exist for different types of wear to determine the amount of material removal during a specified time period under well-defined conditions. ASTM International Committee G-2 standardizes wear testing for specific applications, which are periodically updated. The Society for Tribology and Lubrication Engineers (STLE) has documented a large number of frictional, wear and lubrication tests. Standardized wear tests are used to create comparative material rankings for

5616-862: The data transfer and power delivery functionality with ... 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. 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. 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. USB also provides power to peripheral devices;

5720-493: The delays from connecting cables, the maximum acceptable delay per cable amounts to 26 ns. The USB 2.0 specification requires that cable delay be less than 5.2 ns/m ( 1.6 ns/ft , 192 000 km/s ), which is close to the maximum achievable transmission speed for standard copper wire. 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

5824-434: The density of "surface energy". Most solids will adhere on contact to some extent. However, oxidation films, lubricants and contaminants naturally occurring generally suppress adhesion, and spontaneous exothermic chemical reactions between surfaces generally produce a substance with low energy status in the absorbed species. Adhesive wear can lead to an increase in roughness and the creation of protrusions (i.e., lumps) above

5928-506: The development of USB in 1995: 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. Ajay Bhatt and his team worked on

6032-402: The device during initialization (the period after physical connection called "enumeration") and so are relatively permanent, whereas pipes may be opened and closed. There are two types of pipe: stream and message. 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

6136-400: 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

6240-425: The erosive wear on the inclination angle and material properties is provided in. For a given particle morphology, the erosion rate, E {\displaystyle E} , can be fit with a power law dependence on velocity: E = k v n {\displaystyle E=kv^{n}} where k {\displaystyle k} is a constant, v {\displaystyle v}

6344-432: The following ECNs: A USB system consists of a host with one or more downstream facing ports (DFP), 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. USB devices are linked in series through hubs. The hub built into

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6448-561: The four contacts in standard-size USB connectors. This ID pin is connected to GND in Type-A plugs, and left unconnected in Type-B plugs. Typically, a pull-up resistor in the device is used to detect the presence or absence of an ID connection. The OTG device with the A-plug inserted is called the A-device and is responsible for powering the USB interface when required, and by default assumes

6552-421: The general backward compatibility of USB 3.0 as shown. Manufacturers of personal electronic devices might not include a USB standard connector on their product for technical or marketing reasons. E.g. Olympus has been using a special cable called CB-USB8 one end of which has a special contact. Some manufacturers provide proprietary cables, such as Lightning , that permit their devices to physically connect to

6656-448: The host controller is called the root hub . 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

6760-964: 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) ). 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. 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. USB connectors have been increasingly replacing other types of charging cables for portable devices. USB connector interfaces are classified into three types:

6864-414: The less expensive cable would bear the most wear . In standard USB, the electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is usually protected by an enclosing metal shell. The shell on the plug makes contact with the receptacle before any of the internal pins. The shell is typically grounded, to dissipate static electricity and to shield

6968-520: The manner of material removal. Several different mechanisms have been proposed to describe the manner in which the material is removed. Three commonly identified mechanisms of abrasive wear are: Plowing occurs when material is displaced to the side, away from the wear particles, resulting in the formation of grooves that do not involve direct material removal. The displaced material forms ridges adjacent to grooves, which may be removed by subsequent passage of abrasive particles. Cutting occurs when material

7072-614: 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. 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

7176-554: The maximum power may not always be available from the upstream port. USB 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

7280-520: The maximum practical length is 3 metres (9 ft 10 in). Downstream USB connectors supply power at a nominal 5 V DC via the V_BUS pin to upstream USB devices. The tolerance on V_BUS at an upstream (or host) connector was originally ±5% (i.e. could lie anywhere in the range 4.75 V to 5.25 V). With the release of the USB Type-C specification in 2014 and its 3 A power capability,

7384-596: 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 . USB 3.2 , released in September 2017, 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

7488-423: The mechanical characteristics of Micro-A plugs , Micro-AB receptacles (which accept both Micro-A and Micro-B plugs), Double-Sided Micro USB, and Micro-B plugs and receptacles, along with a Standard-A receptacle to a Micro-A plug adapter. Micro-USB was endorsed as the standard connector for data and power on mobile devices by the cellular phone carrier group Open Mobile Terminal Platform (OMTP) in 2007. Micro-USB

7592-855: The nature of disturbance at the worn surface or "mechanism", and whether it effects a self regenerative or base layer. Wear mechanisms are the physical disturbance. For example, the mechanism of adhesive wear is adhesion . Wear mechanisms and/or sub-mechanisms frequently overlap and occur in a synergistic manner, producing a greater rate of wear than the sum of the individual wear mechanisms. Adhesive wear can be found between surfaces during frictional contact and generally refers to unwanted displacement and attachment of wear debris and material compounds from one surface to another. Two adhesive wear types can be distinguished: Generally, adhesive wear occurs when two bodies slide over or are pressed into each other, which promote material transfer. This can be described as plastic deformation of very small fragments within

7696-508: 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. Starting with the USB 3.2 specification, USB-IF introduced a new naming scheme. To help companies with the branding of the different operation modes, USB-IF recommended branding

7800-414: The nominal voltage above 5 V. USB PD continues the use of the bilateral 5% tolerance, with allowable voltages of PDO ±5% ±0.5 V (eg. for a PDO of 9.0 V, the maximum and minimum limits are 9.95 V and 8.05 V, respectively). There are several minimum allowable voltages defined at different locations within a chain of connectors, hubs, and cables between an upstream host (providing

7904-452: The number of a host's ports. 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. 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. USB has since evolved into

8008-537: 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. Each USB connection

8112-528: The optional functionality as Thunderbolt 4 products. USB4 2.0 with 80 Gbit/s speeds was to be revealed in November 2022. Further technical details were to be released at two USB developer days scheduled for November 2022. The USB4 specification states that the following technologies shall be supported by USB4: Because of the previous confusing naming schemes, USB-IF decided to change it once again. As of 2 September 2022, marketing names follow

8216-561: The original surface. In industrial manufacturing, this is referred to as galling , which eventually breaches the oxidized surface layer and connects to the underlying bulk material, enhancing the possibility for a stronger adhesion and plastic flow around the lump. A simple model for the wear volume for adhesive wear, V {\displaystyle V} , can be described by: V = K W L H v {\displaystyle V=K{\frac {WL}{H_{v}}}} where W {\displaystyle W}

8320-532: 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. A group of seven companies began

8424-468: The power) and a downstream device (consuming the power). To allow for voltage drops, the voltage at the host port, hub port, and device are specified to be at least 4.75 V, 4.4 V, and 4.35 V respectively by USB 2.0 for low-power devices, but must be at least 4.75 V at all locations for high-power devices (however, high-power devices are required to operate as a low-powered device so that they may be detected and enumerated if connected to

8528-411: The properties of the surface being eroded. The impingement angle is one of the most important factors and is widely recognized in literature. For ductile materials, the maximum wear rate is found when the impingement angle is approximately 30°, whilst for non-ductile materials the maximum wear rate occurs when the impingement angle is normal to the surface. A detailed theoretical analysis of dependency of

8632-540: The receptacle. By design, it is 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. 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 other connectors use. The different A and B plugs prevent accidentally connecting two power sources. However, some of this directed topology

8736-613: The role of host. The OTG device with the B-plug inserted is called the B-device and by default assumes the role of peripheral. An OTG device with no plug inserted defaults to acting as a B-device. If an application on the B-device requires the role of host, then the Host Negotiation Protocol (HNP) is used to temporarily transfer the host role to the B-device. OTG devices attached either to a peripheral-only B-device or

8840-488: The side of it. In this way, cables with smaller 5 pin USB 2.0 Micro-B plugs can be plugged into devices with 10 contact USB 3.0 Micro-B receptacles and achieve backward compatibility. USB cables exist with various combinations of plugs on each end of the cable, as displayed below in the USB cables matrix . USB On-The-Go (OTG) introduces the concept of a device performing both host and device roles. All current OTG devices are required to have one, and only one, USB connector:

8944-402: The small particles removed by wear are oxidized in air. The oxides are usually harder than the underlying metal, so wear accelerates as the harder particles abrade the metal surfaces further. Fretting corrosion acts in the same way, especially when water is present. Unprotected bearings on large structures like bridges can suffer serious degradation in behaviour, especially when salt is used during

9048-438: The specification), SuperSpeed (from version 3.0), and SuperSpeed+ (from version 3.1). The modes have differing hardware and cabling requirements. USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specification suggests that plugs and receptacles be color-coded (SuperSpeed is identified by blue). The connectors

9152-489: The standard at Intel; the first integrated circuits supporting USB were produced by Intel in 1995. 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 ). 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

9256-479: The standard extend the power delivery limits for battery charging and devices requiring up to 240 watts . USB has been selected as the standard charging format for many mobile phones , reducing the proliferation of proprietary chargers. Unlike other data buses (such as Ethernet ), USB connections are directed; a host device has "downstream" facing ports that connect to the "upstream" facing ports of devices. Only downstream facing ports provide power; this topology

9360-434: 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

9464-498: The surface layers. The asperities or microscopic high points ( surface roughness ) found on each surface affect the severity of how fragments of oxides are pulled off and added to the other surface, partly due to strong adhesive forces between atoms, but also due to accumulation of energy in the plastic zone between the asperities during relative motion. The type of mechanism and the amplitude of surface attraction varies between different materials but are amplified by an increase in

9568-453: The surface through repeated deformations and cutting actions. It is a widely encountered mechanism in industry. Due to the nature of the conveying process, piping systems are prone to wear when abrasive particles have to be transported. The rate of erosive wear is dependent upon a number of factors. The material characteristics of the particles, such as their shape, hardness, impact velocity and impingement angle are primary factors along with

9672-481: The syntax "USB  x Gbps", where x is the speed of transfer in Gbit/s. Overview of the updated names and logos can be seen in the adjacent table. 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. This version incorporates

9776-415: 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

9880-489: 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. SuperSpeed's architecture

9984-468: The type of hardware: host, peripheral device, or hub. 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

10088-470: The unused area of the original 4 pin USB 1.0 design, making USB 3.0 Type-A plugs and receptacles backward compatible to those of USB 1.0. On the device side, a modified Micro-B plug (Micro-B SuperSpeed) is used to cater for the five additional pins required to achieve the USB 3.0 features (USB-C plug can also be used). The USB 3.0 Micro-B plug effectively consists of a standard USB 2.0 Micro-B cable plug, with an additional 5 pins plug "stacked" to

10192-640: The wear groove, resulting in additional material removal by spalling . Abrasive wear can be measured as loss of mass by the Taber Abrasion Test according to ISO 9352 or ASTM D 4060. The wear volume for single-abrasive wear, V {\displaystyle V} , can be described by: V = α β W L H v = K W L H v {\displaystyle V=\alpha \beta {\frac {WL}{H_{v}}}=K{\frac {WL}{H_{v}}}} where W {\displaystyle W}

10296-579: The winter to deice the highways carried by the bridges. The problem of fretting corrosion was involved in the Silver Bridge tragedy and the Mianus River Bridge accident. Erosive wear can be defined as an extremely short sliding motion and is executed within a short time interval. Erosive wear is caused by the impact of particles of solid or liquid against the surface of an object. The impacting particles gradually remove material from

10400-654: The wires within the connector. The USB standard specifies tolerances for compliant USB connectors to minimize physical incompatibilities in connectors from different vendors. The USB specification also defines limits to the size of a connecting device in the area around its plug, so that adjacent ports are not blocked. Compliant devices must either fit within the size restrictions or support a compliant cable that does. USB 2.0 uses two wires for power (V BUS and GND), and two for differential serial data signals . Mini and micro connectors have their GND connections moved from pin #4 to pin #5, while their pin #4 serves as an ID pin for

10504-490: Was chosen to easily prevent electrical overloads and damaged equipment. Thus, USB cables have different ends: A and B, with different physical connectors for each. Each format has a plug and receptacle defined for each of the A and B ends. A USB cable, by definition, has a plug on each end—one A (or C) and one B (or C)—and the corresponding receptacle is usually on a computer or electronic device. The mini and micro formats may connect to an AB receptacle, which accepts either an A or

10608-648: Was embraced as the "Universal Charging Solution" by the International Telecommunication Union (ITU) in October 2009. In Europe, micro-USB became the defined common external power supply (EPS) for use with smartphones sold in the EU, and 14 of the world's largest mobile phone manufacturers signed the EU's common EPS Memorandum of Understanding (MoU). Apple , one of the original MoU signers, makes Micro-USB adapters available—as permitted in

10712-524: Was released on 1 September 2022 by the USB Implementers Forum. USB4 is based on the Thunderbolt 3 protocol. It supports 40 Gbit/s throughput, is compatible with Thunderbolt 3, and backward compatible with USB 3.2 and USB 2.0. 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. During CES 2020 , USB-IF and Intel stated their intention to allow USB4 products that support all

10816-434: Was the earliest revision that was widely adopted and led to what Microsoft designated the " Legacy-free PC ". 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

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