rajpurkar/squad huggingface dataset:
Title: USB

In general, USB cables have only plugs on their ends, while hosts and devices have only receptacles. Hosts almost universally have Type-A receptacles, while devices have one or another Type-B variety. Type-A plugs mate only with Type-A receptacles, and the same applies to their Type-B counterparts; they are deliberately physically incompatible. However, an extension to the USB standard specification called USB On-The-Go (OTG) allows a single port to act as either a host or a device, which is selectable by the end of the cable that plugs into the receptacle on the OTG-enabled unit. Even after the cable is hooked up and the units are communicating, the two units may "swap" ends under program control. This capability is meant for units such as PDAs in which the USB link might connect to a PC's host port as a device in one instance, yet connect as a host itself to a keyboard and mouse device in another instance.

Question: USB cables and device have only what on their ends?
Answer: plugs

Question: Hosts and devices only have what in terms of connecting to a USB device?
Answer: receptacles

Question: Devices usually have what type of receptacle?
Answer: one or another Type-B variety

Question: Hosts almost always have what type of receptacle?
Answer: Type-A receptacles
Title: USB

Various connectors have been used for smaller devices such as digital cameras, smartphones, and tablet computers. These include the now-deprecated (i.e. de-certified but standardized) mini-A and mini-AB connectors; mini-B connectors are still supported, but are not OTG-compliant (On The Go, used in mobile devices). 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; the mini-A connector and the mini-AB receptacle connector were deprecated on 23 May 2007.

Question: What has been used to connect digital cameras. smartphones and other devices to tablet computers?
Answer: Various connectors

Question: What was standard for transferring data to and from the earlier type of smartphones?
Answer: The mini-B USB connector

Question: How large are both mini-A and mini-B plugs?
Answer: approximately 3 by 7 mm

Question: When were the mini-A connector and and the mini-AB receptacle connector depreceated?
Answer: 23 May 2007
Title: USB

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 the mechanical characteristics of micro-A plugs, micro-AB receptacles (which accept both micro-A and micro-B plugs), and micro-B plugs and receptacles, along with a standard-A receptacle to micro-A plug adapter.

Question: What is the micro connector designed for?
Answer: to reduce the mechanical wear on the device

Question: What is the easier-to-replace cable designed for?
Answer: to bear the mechanical wear of connection and disconnection

Question: What is the micro-plug rated for?
Answer: 10,000 connect-disconnect cycles
Title: USB

The cellular phone carrier group Open Mobile Terminal Platform (OMTP) in 2007 endorsed micro-USB as the standard connector for data and power on mobile devices In addition, on 22 October 2009 the International Telecommunication Union (ITU) has also announced that it had embraced micro-USB as the Universal Charging Solution its "energy-efficient one-charger-fits-all new mobile phone solution," and added: "Based on the Micro-USB interface, UCS chargers also include a 4-star or higher efficiency rating—​​up to three times more energy-efficient than an unrated charger."

Question: In 2007 who endorsed micro-USB as the standard connector for data and power on mobile devices?
Answer: The cellular phone carrier group Open Mobile Terminal Platform

Question: When did the ITU announce that it had embraced micro-USB as the Universal Charging Solution?
Answer: 22 October 2009

Question: What has energy-efficient one-charger-fits-all new mobile phone solution?
Answer: micro-USB
Title: USB

The European Standardisation Bodies CEN, CENELEC and ETSI (independent of the OMTP/GSMA proposal) defined a common External Power Supply (EPS) for use with smartphones sold in the EU based on micro-USB. 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 the Common EPS MoU – for its iPhones equipped with Apple's proprietary 30-pin dock connector or (later) Lightning connector.

Question: Who defined a common External Power Supply for use with smartphones sold?
Answer: The European Standardisation Bodies CEN, CENELEC and ETSI

Question: How many mobile phone manufacturers signed the EU's common EPS (MoU)?
Answer: 14

Question: Who was one of the original MoU signers?
Answer: Apple
Title: USB

All current USB On-The-Go (OTG) devices are required to have one, and only one, USB connector: a micro-AB receptacle. Non-OTG compliant devices are not allowed to use the micro-AB receptacle, due to power supply shorting hazards on the VBUS line. The micro-AB receptacle is capable of accepting both 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. Prior to the development of micro-USB, USB On-The-Go devices were required to use mini-AB receptacles to perform the equivalent job.

Question: What are all USB On-The-Go devices required to have?
Answer: one, and only one, USB connector

Question: Non-OTG compliant devices are not allowed to use what?
Answer: the micro-AB receptacle

Question: Why are the Non-OTG compliant devices not allowed to use the micro-AB receptacle?
Answer: power supply shorting hazards on the VBUS line
Title: USB

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 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.

Question: The OTG device with the B-plug inserted is called what?
Answer: B-device

Question: What does an OTG device default to with no plug inserted?
Answer: to acting as a B-device

Question: What is the A-device responsible for?
Answer: powering the USB interface when required
Title: USB

USB is a serial bus, using four shielded wires for the USB 2.0 variant: two for power (VBUS and GND), and two for differential data signals (labelled as D+ and D− in pinouts). Non-Return-to-Zero Inverted (NRZI) encoding scheme is used for transferring data, with a sync field to synchronize the host and receiver clocks. D+ and D− signals are transmitted on a twisted pair, providing half-duplex data transfers for USB 2.0. 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 the On-The-Go host/client identification.

Question: What is USB?
Answer: a serial bus

Question: What kind of wires does the USB 2.0 variant use?
Answer: four shielded wires

Question: What are the four shielded wires in the USB 2.0 variant used for?
Answer: two for power (VBUS and GND), and two for differential data signals
Title: USB

USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi 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 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 per meter (192 000 km/s, which is close to the maximum achievable transmission speed for standard copper wire).

Question: How long is the maximum cable length the USB 2.0 provides?
Answer: 5 meters for devices running at Hi Speed

Question: What is the maximum acceptable delay per cable?
Answer: 26 ns

Question: What does theUSB 2.0 specification require?
Answer: cable delay be less than 5.2 ns per meter
Title: USB

A unit load is defined as 100 mA in USB 1.x and 2.0, and 150 mA in USB 3.0. A device may draw a maximum of five unit loads from a port in USB 1.x and 2.0 (500 mA), or six unit loads in USB 3.0 (900 mA). There are two types of devices: low-power and high-power. A low-power device (such as a USB HID) draws at most one-unit load, with minimum operating voltage of 4.4 V in USB 2.0, and 4 V in USB 3.0. A high-power device draws, at most, the maximum number of unit loads the standard permits. Every device functions initially as low-power (including high-power functions during their low-power enumeration phases), but may request high-power, and get it if available on the providing bus.

Question: What is a unit load defined as?
Answer: 100 mA in USB 1.x and 2.0

Question: How much is a unit load in USB 3.0?
Answer: 150 mA

Question: What is the maximum amount of load a USB 1. and 2.0 device may draw?
Answer: five unit loads

Question: What is the maximum amount of load a USB 3.0 device may draw?
Answer: six unit loads
Title: USB

Some devices, such as high-speed external disk drives, require more than 500 mA of current and therefore may have power issues if powered from just one USB 2.0 port: erratic function, failure to function, or overloading/damaging the port. Such devices may come with an external power source or a Y-shaped cable that has two USB connectors (one for power and data, the other for power only) to plug into a computer. With such a cable, a device can draw power from two USB ports simultaneously. However, USB compliance specification states that "use of a 'Y' cable (a cable with two A-plugs) is prohibited on any USB peripheral", meaning that "if a USB peripheral requires more power than allowed by the USB specification to which it is designed, then it must be self-powered."

Question: What is an example of a device that requires more than 500 mA of current?
Answer: high-speed external disk drives

Question: What is an issue that may occur if a high-speed external disk drive is powered from just one USB 2.0 port.
Answer: may have power issues

Question: What does USB compliance specification prohibit?
Answer: "use of a 'Y' cable (a cable with two A-plugs)
Title: USB

The USB Battery Charging Specification Revision 1.1 (released in 2007) defines a new type of USB port, called the charging port. Contrary to the standard downstream port, for which current draw by a connected portable device can exceed 100 mA only after digital negotiation with the host or hub, a charging port can supply currents between 500 mA and 1.5 A without the digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drops its output voltage if the portable device attempts to draw more than the rated current. The charger port may shut down if the load is too high.

Question: What defines a new type of USB port, called the charging port?
Answer: The USB Battery Charging Specification Revision 1.1

Question: When was the USB Battery Charging Specification Revision 1.1 released?
Answer: in 2007

Question: What was the USB Battery Charging Specification Revision 1.1 called?
Answer: the charging port

Question: What does a charging port supply?
Answer: up to 500 mA at 5 V
Title: USB

Two types of charging port exist: the charging downstream port (CDP), supporting data transfers as well, and the dedicated charging port (DCP), without data support. A portable device can recognize the type of USB port; on a dedicated charging port, the D+ and D− pins are shorted with a resistance not exceeding 200 ohms, while charging downstream ports provide additional detection logic so their presence can be determined by attached devices. (see ref pg. 2, Section 1.4.5, & Table 5-3 "Resistances"—pg. 29).

Question: How many types of charging ports exist?
Answer: Two types

Question: What can a portable device recognize?
Answer: the type of USB port

Question: What are the D+ and D- shortened with?
Answer: a resistance not exceeding 200 ohms
Title: USB

The USB Battery Charging Specification Revision 1.2 (released in 2010) makes clear that there are safety limits to the rated current at 5 A coming from USB 2.0. On the other hand, several changes are made and limits are increasing including allowing 1.5 A on charging downstream ports for unconfigured devices, allowing high speed communication while having a current up to 1.5 A, and allowing a maximum current of 5 A. Also, revision 1.2 removes support for USB ports type detection via resistive detection mechanisms.

Question: What does the USB Battery Charging Specification Revision 1.2 make clear of?
Answer: there are safety limits to the rated current at 5 A coming from USB 2.0

Question: What does revision 1.2 remove?
Answer: USB ports type detection via resistive detection mechanisms

Question: When was USB Battery Charging Specification Revision 1.2 released?
Answer: in 2010
Title: USB

In July 2012, the USB Promoters Group announced the finalization of the USB Power Delivery ("PD") specification, an extension that specifies using certified "PD aware" USB cables with standard USB Type-A and Type-B connectors to deliver increased power (more than 7.5 W) to devices with larger power demand. Devices can request higher currents and supply voltages from compliant hosts –  up to 2 A at 5 V (for a power consumption of up to 10 W), and optionally up to 3 A or 5 A at either 12 V (36 W or 60 W) or 20 V (60 W or 100 W). In all cases, both host-to-device and device-to-host configurations are supported.

Question: When did the USB Promoters Group announce the finalization of the USB Power Delivery specification?
Answer: In July 2012

Question: What can devices request?
Answer: higher currents and supply voltages from compliant hosts

Question: In all cases, both host-to-device and device-to-host configurations are what?
Answer: supported
Title: USB

The USB Power Delivery revision 2.0 specification has been released as part of the USB 3.1 suite. It covers the Type-C cable and connector with four power/ground pairs and a separate configuration channel, which now hosts a DC coupled low-frequency BMC-coded data channel that reduces the possibilities for RF interference. Power Delivery protocols have been updated to facilitate Type-C features such as cable ID function, Alternate Mode negotiation, increased VBUS currents, and VCONN-powered accessories.

Question: The USB Power Delivery revision 2.0 specification has been released as part of what?
Answer: USB 3.1

Question: What does the USB Power Delivery revision 2.0 specification cover?
Answer: Type-C cable and connector with four power/ground pairs and a separate configuration channel

Question: Power delivery protocols have been updated to facilitate what?
Answer: Type-C features
Title: USB

Sleep-and-charge USB ports can be used to charge electronic devices even when the computer is switched off. Normally, when a computer is powered off the USB ports are powered down, preventing phones and other devices from charging. Sleep-and-charge USB ports remain powered even when the computer is off. On laptops, charging devices from the USB port when it is not being powered from AC drains the laptop battery faster; most laptops have a facility to stop charging if their own battery charge level gets too low.

Question: What can sleep-and-charge USB ports be used to do?
Answer: charge electronic devices even when the computer is switched off

Question: What is normally powered off whenever the computer is off?
Answer: USB ports

Question: What remain powered even whenever the computer is powered off?
Answer: Sleep-and-charge USB ports
Title: USB

On Dell and Toshiba laptops, the port is marked with the standard USB symbol with an added lightning bolt icon on the right side. Dell calls this feature PowerShare, while Toshiba calls it USB Sleep-and-Charge. On Acer Inc. and Packard Bell laptops, sleep-and-charge USB ports are marked with a non-standard symbol (the letters USB over a drawing of a battery); the feature is simply called Power-off USB. On some laptops such as Dell and Apple MacBook models, it is possible to plug a device in, close the laptop (putting it into sleep mode) and have the device continue to charge.[citation needed]

Question: On what laptops are the USB ports marked with a USB symbol with an added lightening bolt icon?
Answer: On Dell and Toshiba laptops

Question: What does dell call the feature that lets USB drives to remain powered when the computer is off?
Answer: PowerShare

Question: On what laptops are the sleep-and-charge marked with a non-standard symbol?
Answer: On Acer Inc. and Packard Bell laptops
Title: USB

The GSM Association (GSMA) followed suit on 17 February 2009, and on 22 April 2009, this was further endorsed by the CTIA – The Wireless Association, with the International Telecommunication Union (ITU) announcing on 22 October 2009 that it had also embraced the Universal Charging Solution as its "energy-efficient one-charger-fits-all new mobile phone solution," and added: "Based on the Micro-USB interface, UCS chargers will also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger."

Question: When did the GSM Association follow suit?
Answer: 17 February 2009

Question: UCS chargers will also include what?
Answer: a 4-star or higher efficiency rating

Question: When was this further endorsed by the CTIA?
Answer: 22 April 2009
Title: USB

In June 2009, many of the world's largest mobile phone manufacturers signed an EC-sponsored Memorandum of Understanding (MoU), agreeing to make most data-enabled mobile phones marketed in the European Union compatible with a common External Power Supply (EPS). The EU's common EPS specification (EN 62684:2010) references the USB Battery Charging standard and is similar to the GSMA/OMTP and Chinese charging solutions. In January 2011, the International Electrotechnical Commission (IEC) released its version of the (EU's) common EPS standard as IEC 62684:2011.

Question: When did many of the largest mobile phone manufacturers sign an EC-sponsored MoU?
Answer: June 2009

Question: What did the MoU make the manufacturers agree to do?
Answer: to make most data-enabled mobile phones marketed in the European Union compatible with a common External Power Supply

Question: When did the IEC release its version of the common EPS standard as IEC 62684:2011?
Answer: January 2011
Title: USB

Some USB devices require more power than is permitted by the specifications for a single port. This is common for external hard and optical disc drives, and generally for devices with motors or lamps. Such devices can use an external power supply, which is allowed by the standard, or use a dual-input USB cable, one input of which is used for power and data transfer, the other solely for power, which makes the device a non-standard USB device. Some USB ports and external hubs can, in practice, supply more power to USB devices than required by the specification but a standard-compliant device may not depend on this.

Question: Some USB devices require what?
Answer: more power than is permitted by the specifications for a single port.

Question: Some devices such as an external hard and optical disk drive can use what?
Answer: an external power supply

Question: What is another alternative for power for an external hard and optical disk drive?
Answer: a dual-input USB cable

Question: What is the purpose of a dual-input USB cable?
Answer: one input of which is used for power and data transfer, the other solely for power
Title: USB

In addition to limiting the total average power used by the device, the USB specification limits the inrush current (i.e., that used to charge decoupling and filter capacitors) when the device is first connected. Otherwise, connecting a device could cause problems with the host's internal power. USB devices are also required to automatically enter ultra low-power suspend mode when the USB host is suspended. Nevertheless, many USB host interfaces do not cut off the power supply to USB devices when they are suspended.

Question: What does the USB specification limit?
Answer: the inrush current

Question: When is the inrush current affected by the USB specification?
Answer: when the device is first connected

Question: What are USB devices required to enter?
Answer: ultra low-power suspend mode when the USB host is suspended

Question: Many USB host interfaces do not what?
Answer: cut off the power supply to USB devices when they are suspended
Title: USB

Some non-standard USB devices use the 5 V power supply without participating in a proper USB network, which negotiates power draw with the host interface. These are usually called USB decorations.[citation needed] Examples include USB-powered keyboard lights, fans, mug coolers and heaters, battery chargers, miniature vacuum cleaners, and even miniature lava lamps. In most cases, these items contain no digital circuitry, and thus are not standard compliant USB devices. This may cause problems with some computers, such as drawing too much current and damaging circuitry. Prior to the Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host, which then permits the device to switch into high-power mode.

Question: What do some non-standard USB devices use?
Answer: the 5 V power supply without participating in a proper USB network

Question: What Negotiates power draw with the host interface?
Answer: the 5 V power supply

Question: What does the USB specification require prior to the Battery Charging Specification?
Answer: that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host
Title: USB

USB data is transmitted by toggling the data lines between the J state and the opposite K state. USB encodes data using the NRZI line coding; a 0 bit is transmitted by toggling the data lines from J to K or vice versa, while a 1 bit is transmitted by leaving the data lines as-is. To ensure a minimum density of signal transitions remains in the bitstream, USB uses bit stuffing; an extra 0 bit is inserted into the data stream after any appearance of six consecutive 1 bits. Seven consecutive received 1 bits is always an error. USB 3.0 has introduced additional data transmission encodings.

Question: How is the USB data transmitted?
Answer: by toggling the data lines between the J state and the opposite K state

Question: What does USB use to encode data?
Answer: the NRZI line coding

Question: To ensure a minimum density of signal transitions  remains in the bitsream, what does USB use?
Answer: bit stuffing
Title: USB

A USB packet's end, called EOP (end-of-packet), is indicated by the transmitter driving 2 bit times of SE0 (D+ and D− both below max.) and 1 bit time of J state. After this, the transmitter ceases to drive the D+/D− lines and the aforementioned pull up resistors hold it in the J (idle) state. Sometimes skew due to hubs can add as much as one bit time before the SE0 of the end of packet. This extra bit can also result in a "bit stuff violation" if the six bits before it in the CRC are 1s. This bit should be ignored by receiver.

Question: What is a USB packet's end called?
Answer: EOP (end-of-packet)

Question: What can skew due to hubs add?
Answer: as much as one bit time before the SE0 of the end of packet

Question: What can this extra bit result in?
Answer: "bit stuff violation