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NOTE:  Items highlighted in RED are defined elsewhere in this Glossary, while items highlighted in BLUE are site links for further information.

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USB:  UniverCerftified USB logosal Serial Bus (see BUS, above), a common port on a computer into which can be plugged (up to 127) peripheral devices (like drives, printers, keyboards, mice, modems, etc.). The 127 comes from the fact that there is a 7-bit address field and, in reality, you wouldn’t be able to daisy-chain 127 devices together anyway.  The protocol, connectors, ports and cables were first released in 1996 and were designed by a collaboration of 7 companies, including Intel, Compaq, DEC, IBM & Microsoft.  Especially since more and more computers now no longer use PS/2 ports to connect keyboards and mice, and most peripherals like printers (which started with parallel ports) and external drives (which used to used standard serial ports), USB ports, connectors and communications protocols are now that much more popular. 

USB comes in 3 specifications and speeds:USB 1” (1996 - only found on very old computers; low speed (1.5Mbit/s) and full speed (12Mbits/s)), “USB 2” (2000 -quite common; 480 Mbit/s) and “USB 3” (2008 - dubbed “Superspeed” found only on USB 3 devices, which are becoming much more common; up to 5Gbits/s) [See SPEED]  Basically, USB2 is about ten times faster than USB1, and USB3 is about  ten times faster than USB2.  For more about USB 3 (which is distinguished by its blue port and USB 3 logoupdated logo (which is slightly different for each computer manufacturer) at left), click HERE. For devices requiring limited power, the USB port is perfect, as it provides only about 5 volts of power (which is still sufficient to short out a device or board if you’re not careful) and has four “pins” in the connector.  USB 3.1 raises USB’s total data bandwidth from 3.0’s 5 gigabits per second to 10 Gbps. 

A newly ratified Power over USB has beeWireless USB smalln ratified increasing up to 100 watts over the standard 10 watts.  Really want to know more about the USB standard, click HERE.  And there’s also Wireless USB, which certifies wireless products that can be used with wireless hubs and the like. Click HERE for photos of the various connectors.  The downside is that only the newer devices and boards support these new specs. And assure that you have the correct connectors, ports and cables for each; although the specifications are usually backward-compatible, there are connector and port incompatibilities that can prevent your using the newer connections.

In this regard, USB 1, 2 and 3 cables and connectors look pretty much the same (except USB 3 usually has a blue port, see connectors).  Then there are the smaller Micro and Mini USB connectors and ports, both featuring 5 pins, used mostly for portable device chargers (like cellphones and pads).  The Mini USB was the first universally accepted mobile charging and data transfer interface, but later the Micro USB was introduced as a thinner and faster version of the Mini USB and has since become the predominant interface of the two. Developed by the USB Implementers Forum (see Associations) starting in 2007, another reason it became so popular was that it allows for USB OTG (“On-The-Go”) format (see below, by using the 5th pin, which is not used in Mini-USB), which is a specification that allows devices like mobile phones to act like a host, allowing a USB drive, mouse, keyboard or other peripherals to be attached and used.  

In 2015, the USB Type C connector (not the controller, which actually determines the speed) was introduced (though it was ratified in late 2014 by the USBIF).  It is reversible (can be installed up or down) and backward compatible from USB 2 & 3. And it can deliver huge amounts of power and data very quickly.  [Again, see connectors for photos.]  USB OTG BUT BE VERY CAREFUL:  It can destroy your laptop or other device.  If you select a cheap cable, it can (by design) start drawing too much power, overheating the device and potentially destroying it.  The ports on most laptops aren’t designed to handle delivering that much power.  The more expensive cables, those certified by the USB Implementers Forum (see Associations).

Finally, let’s not forget USB OTG, or USB on-the-go, which allows a device like a flash drive fitted with a micro-USB adapter to transfer files between smart phones and a flash drive (see photo at right).  USB OTG introduces the concept of a device performing as both a “master” and a “slave” whenever two devices are connected and one of them is a USB OTG device to that flash drives, digital cameras, mice and keyboards can switch back and forth between the roles of host an device, although they will present themselves as a USB Mass Storage Device in the device manager when connected to the host computer.  This is much different than the standard USB architecture, where the master (“host” or “A” device sets up communications with the peripheral (“B”) device and handles service provisioning (data communication, power and file managing), while the peripheral device does little of the heavy lifting.  In doing so, USB OTG introduced three new communication protocols, the ADP (Attach Detection Protocol), SRP (Session Request Protocol) and the HNP (Host Negotiation Protocol).  USB OTG has its own plugs and micro/mini plugs and is also backward compatible.

The inventor? Remember the summer 2009 Intel commercial where co-inventor of the USB,  Ajay Bhatt (actually an actor, Ajay was far too busy, says Intel) is treated like a superstar?  At least we Ajay Bhatknow one of the co-inventors.  The universal USB symbol is shown at left.  The symbol, created at the time of the USB 1.0 spec, was drawn to resemble Neptune’s Trident (the Dreizack [pronounced “dry-zack”]), but instead of three even triangle tips, it is designed with a triangle, circle and square at its uneven tips, claimed to be representative of the three different (never defined) types of peripherals that could be attached using the standard. (On Neptune’s Trident, the meaning is significantly different:  The three prongs on the pitchfork stand for “becoming, being and passing away,” which makes no sense in the context of computer connections. Born, living, dying??)

Finally, remember that just because you have a particular version of USB, it doesn’t mean that the connection is actually working at the highest speed.  The speed can be influenced by a number of factors, including the slowest device that may be connected to a hub, as USB (like a network) can only be as fast as its slowest link, bad cables, or driver or O/S setting issues.  If you believe that your speeds are too slow, and you are somewhat technical, there are available software tools from Microsoft for you to detect the actual throughput of your connection.  The USBview tool (part of the Windows De-bugging Toolkit, you must match the version to the bittedness of your system) can be a little difficult to decipher, but it will provide the answer.

USB DEBUGGING: Sometimes referred to as Developer Mode.  This is a feature which establishes a direct connection between an Android device (phone, tablet) and a computer, making it ready for deeper level actions.  It must be enabled, granting administrative level access to the device so that, using Android SDK [Software Development Kit], newly programmed apps can be copied via USB to phones or tablets, or terminal commands may be used to restore a “bricked” Android phone.  Often device manufacturers will use the feature to completely load their blank devices for sale.  Because enabling such a feature will allow your device to be hacked with malware or viruses, it’s always best to leave it disabled, except when it’s necessary to transfer files, apps, programs or updates, after which it should immediately be disabled again. 

BOOTABLE USB DRIVES: USB drives are not inherently bootable.  That is, while you can read and transfer data between the drive and the computer it is connected to, it may not always be able to boot an O/S from the drive (for example, to restore a backup if the computer’s hard drive has become irretrievably damaged) without first preparing the drive to become a bootable device.  This can be done through the computer management console in a working computer, or using a third-party program (like Bootfit) which will “flip a removable bit” making this possible.

For a comparison of USB vs. Firewire, click HERE

For a discussion of the speeds of USB, Firewire, Thunderbolt and other devices click HERE

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