Babbage | Difference Engine

In praise of the humble USB

The ubiquitous connector is making travel easier

By NV | LOS ANGELES

ANYONE lining up at airport security abroad for a direct flight to America while carrying a phone, tablet, laptop or other portable gizmo with a dead battery will have to leave it behind. The Transportation Security Administration (TSA) announced recently that passengers heading for the United States will be required to switch on any electronic device they are carrying with them—to prove it is the genuine item, and not a fake stuffed with explosive. Likewise, passengers travelling to and from the United Kingdom will have to do the same. Other countries high on terrorists’ hit lists are expected to adopt similar measures.

Following previous threats involving explosives hidden in footwear, the TSA has required passengers to remove their shoes when going through airport security, so that they can be X-rayed separately. Liquids in bottles larger than 100 millilitres (3.4 fluid ounces) were banned for similar reasons. The TSA says it has no evidence of bombs being disguised as phones or other electronic devices. The move is an attempt to anticipate possible attacks in the future, rather than react to ones in the past. Whatever, it is going to make international travel an even bigger hassle.

Babbage frequently flies with a collection of mobile phones, not to mention the obligatory laptop, tablet and camera. Rather than pay American carriers’ punitive roaming charges, he buys a cheap pre-paid phone on arrival (if he does not already have one for the country concerned). On departure, the last thing on his mind is unearthing the appropriate plugs and chargers from the suitcase clutter to replenish their batteries before hastening to catch a plane.

The only good news to come out of these charge-it-or-lose-it shenanigans is that battery chargers are at long last becoming standardised. On a recent trip abroad, Babbage finally realised that a single charger (plus an appropriate power-socket adapter) can be used to top up the batteries in his tablet and smartphone as well as a bunch of foreign phones. With their greater thirst for electricity, laptops still need bulky charger blocks that deliver power at 16.5 volts and up. Likewise, digital cameras with removable batteries still require their own wall-warts.

But most phones these days can suck the same five-volt juice from a standard USB (Universal Serial Bus) charger—thanks to their Micro USB charging ports. Even iPhones and iPads can be recharged from the USB adapter, though a special cable is needed to attach them via Apple’s clunkier iOS connector.

With an estimated six billion in use around the world today, the USB port is the most successful computer interface ever invented. Today’s desktop computers have at least four of them, while laptops usually have two, and most other digital devices at least one.

For that, thank Ajay Bhatt, a computer architect and fellow at Intel, who was the first to come up with the idea of a universal port for attaching peripherals to a personal computer. Back in the mid-1990s, with subsequent input from half a dozen other PC firms, the USB interface quickly became the standard connector for attaching keyboards, printers, scanners, pointing devices and video cameras. In so doing, it displaced the parallel and serial ports on PCs, as well as the Apple desktop bus used in Macintosh computers. By daisy-chaining USB hubs together, up to 127 peripherals could be attached to a single USB port.

The most familiar application remains the ubiquitous “thumb drive”, with its non-volatile memory built into the USB plug itself. When they hit the market over a decade ago, thumb drives quickly killed off floppy disks. Today, with gigabyte memory chips inside them, they are even challenging optical drives.

Like many other data cables, a USB connector has a different shaped plug at either end—a full-size A-type upstream at the host end, and a B-type plug downstream, where it attaches to the device. This ensures that power can flow in one direction only—from A-type to B-type connector—and so prevents delicate equipment from being overloaded electrically and damaged.

The B-type connectors come typically in three different shapes and sizes: a squarish connector found mainly on the backs of printers and scanners; a small, trapezoidal Mini-B common on older phones and cameras; and a flatter Micro-B connector used extensively these days on tablets and mobile phones. Exceptions include Apple’s proprietary B-type connector for older iOS devices, and Nikon’s miniature Micro-B connector (known as the UC-E6) for digital cameras.

A USB connector has four pins: two inner ones carrying data, and two outer ones providing 5-volt power. The standard USB port can deliver 0.5 amp, while the latest version of the specification offers up to 0.9 amp. Dedicated connectors used solely for charging batteries provide up to 2.1 amps.

As for speed, the original USB 1.0 could transmit 12 megabits per second. Parallel ports of the day could manage around 150 kilobits per second, while serial ports offered data rates of 57 kilobits per second. With the introduction of USB 2.0 in 2001, the data rate jumped to 480 megabits per second, and then increased a further ten-fold to 4.8 gigabits per second with the introduction of the USB 3.0 standard in 2008. More recently, an extension to the standard has raised the data rate to 10 gigabits per second.

The USB standard owes its success largely to being simple, versatile, cheap, hot-swappable (it can be plugged and unplugged while a computer is running) while being capable of functioning as a power supply as well as a data link. Such features, however, were not unique when the USB was introduced. Other connectors in use during the 1990s offered as much or more.

For instance, the FireWire interface (known technically as IEEE 1394) pioneered by Apple in the late 1980s was faster and capable of delivering more power. All Apple computers from 1999 onwards included FireWire ports. The plug on the upstream end of the connector was asymmetrical and could be inserted only one way—a definite advantage compared with the fumbling caused by the symmetrical casing of a USB plug.

Though technically more than a match for USB, FireWire fell out of favour with computer, camera and consumer-electronics manufacturers. So much so, the late Steve Jobs, Apple's charismatic boss, was forced in 2008 to declare FireWire dead.

How come? Babbage believes it was simply a matter of cost—exacerbated by the proprietary nature of the FireWire standard. Some 260 patents, held by ten different companies, were involved in its design, all of which had to be licensed by would-be manufacturers. Pooling the patents and authorising an administrator (MPEG LA) to negotiate licensing deals certainly helped. But manufacturers still had to fork out 25 cents for every FireWire device they produced. By contrast, Intel and its co-developers made the cheap USB plug and socket an open standard, available to manufacturers everywhere free of all royalty charges and licensing fees.

Getting back to travelling with multiple phones, tablets and e-readers, many may wonder whether plugging an Android phone into a dedicated USB charger designed for, say, an Apple iPad would blow its brains out. After all, there is a big difference between a USB port rated at 0.5 amp and a dedicated USB charger capable of delivering 2.1 amps.

The short answer is no. Any USB device can be plugged into any USB port, says Extreme Tech. A more powerful charger than the one that came with the device should simply recharge it faster. A longer answer is that it all depends on the age of the device in question. There is no problem with modern gadgets, but the recharging trick may not work with older machines, though it is unlikely to destroy them. Some vintage devices may need to be recharged from a computer running the appropriate driver software.

So, from now on, Babbage intends packing just a dedicated USB charger, while leaving the rat’s nest of cables and wall-warts at home. He just hopes he remembers to top up all the batteries before heading for the plane.

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