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Digital superhighways
(1) The fast-growing number of fax machines, computer modems, and new telephone users demands transmission lines that can handle far greater numbers of calls than traditional copper. This demand is being met by fiber-optic cables, which carry digital messages in the form of rapid bursts of intense laser light.
(2) Capable of carrying hundreds of simultaneous phonecalls down a pair of glass strands, in addition to fax messages, computer data, and television signals, fiber-optic cables are revolutionizing global communication and home entertainment.
(3) Some cable operators already offer a huge choice of channels, interactive games, and even on-demand video films.
(4) Conversations are more intelligible when the two parties can see one another. However, video phones, which make this possible by simultaneously transmitting pictures and speech, are still not widely used.
(5) This is because transmitting a complete video signal requires the sending of more than 200 million bits (units of information) a second 4000 times more than existing cables can handle.
(6) Accepting lower picture quality and using compression, a technique by which redundant or repeated bits of data are omitted, the signal can be reduced to 64,000 bits per second. Even this is beyond the capacity of ordinary telephone lines, so current videophones can be send only crude, still pictures.
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(7) One model, sending data at 14,400 bits per second, takes five seconds to send one still picture.
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THE NEW YORK TIMES
Monday, January 23, 2006
SCIENCE & TECHNOLOGY Greatest New Ideas in the World of Gadgets
By David Pogue
For lovers of gadgets, some of the joys in the year just ended were not new products, but aspects of new products. Here and there, you could even find tiny touches of brilliance: clever steps forward and new additions to old features. Here they are, the five best gadget ideas of 2005. THE VOICE MAIL VCR Voice mail is a delightful invention. But trying to remember which keys to press for replay, skip, delete and so on is not so delightful, especially if you have more than one voice mail system to learn. Thanks to Palm, then, for adding VCR-style buttons on the touch screen of its coming Treo 700W cellphone. You just tap Skip, Play, Delete, or whatever. The phone remembers which touch tones to play so you don't have to.
THE FRONT-SIDE TV CONNECTOR The home-theater explosion is all well and good, except for the tangle of cables. Depending on how permanently your TV has been built into your cabinetry, getting behind it to plug or unplug something is a pain.
Hewlett-Packard's latest microdisplay (rear projection) TV sets solve the problem sweetly and simply: everything plugs into the front. A broad tunnel lets you hand each cable to yourself from the back, an illuminated connection panel makes it easy to see what you're doing at the front, and an attractive door hides the whole ingenious system.
TV A LA CARTE It's always seemed crazy that TV companies would spend $1 million an episode writing and producing a program that is shown only once. Yet the obvious solution making past shows available for purchase on the Internet gave TV executives nightmares of Web pirates run amok.
It took Apple to persuade them to dip a little toe into the Internet waters. The American television network ABC took the first plunge, offering iPod owners five shows' worth of archives for $2 each and no commercials. NBC network came next with broader menu of shows. The concept was a hit, and the era of downloadable, reasonably priced, lightly copyprotected TV episodes is finally upon us.
THE OUTER-BUTTON FLIP PHONE First came the cellphone with a hinge (the flip phone). Then came the flip phone with an external screen, so you could see who was calling. Problem was this arrangement deprived you of the option to dismiss the call or send it to voice mail. If you opened the flip phone to get to the Ignore button, you'd answer the call unless you'd turned off the "opening phone answers the call" feature, in which case you lost one great convenience of having a flip phone to begin with.
The solution? Add buttons on the outside. When a call comes in to the LG VX8100, for example, its external identifies the caller and the small buttons just below it are labeled Ignore (let it ring until voice mail picks up) or Dismiss (send it directly and immediately to voice mail). You get the best of all cellular worlds, without opening the phone.
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THE FREE DOMAIN NAME A domain name is what comes before the ".com" in a Web address like NYTimes.com, verizonwireless.com or Mar- ryMeBritney.com. Getting your own personal dot-com name has its privileges for example, your e-mail address can be You@YourNameHere. com but it costs money and requires some expertise. It took Microsoft, of all companies, to make getting your own dot-com name free. Its new Office Live online software suite for small businesses, now in testing, will offer a domain name, Web site and e-mail accounts free.
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(1) Data Highway
An optical trunk cable comprises a bundle of optical fibers around a thicker strengthening wire, contained in layers of protective sheaths. Each fiber has a core, through which light travels, and a cladding, which contains the light in the core. Both are made from silicon glass, with small amounts of boron or germanium added to improve transmission properties. A plastic sheath around the cladding ensures that no stray light passes into other fibers.
(2) Light Pipes
Optical fibers can transmit digital data in the form of up to 2 billion pulses of laser light a second. This makes them the ideal medium for carrying the rapidly increasing numbers of telephone calls, fax messages, and computer information traveling from place to place. The glass they are made of is so clear that signals can travel for tens of miles before they have to be amplified ten times farther than traditional copper cables.
A fiber is in fact made up of two concentric layers of ultra-pure bubble-free glass. The cylindrical core is surrounded by a cladding drawn from glass with a different refractive index. Laser light shone into the core is confined in a process called total internal reflection rays hitting the boundary between the two layers at a shallow enough angle are reflected rather than escaping.
Because fibers are so thin narrower even than human hair they can be bent quite sharply before light leaks out. input pulse.
(3) Narrow Cables
A pulse of light sent down an optical fiber with a wide core can travel along many alternative paths [A], some involving many more reflections than others. Over long distances the pulse becomes spread out and blurred, eventually merging with the edges of entertainment.
However, in a narrow-core fiber [B], the pulse has only one possible path straight down the center. Blurring of the pulse is greatly reduced and clear signals can therefore be sent over longer distances in such fibers.
(4) Blanket Coverage
A proposed new worldwide telecommunication system based on transmitters in space will have the ability to connect two people anywhere on the globe [E]. The system shown will include 77 satellites, uniformly spaced, 475 miles above the earth and linked by digital signals to form a cellular network.
Subscribers to the system will be able to communicate with any telephone on the terrestrial networks. A call will be routed directly to a satellite from handsets, earphones, or even solar powered phone booths.
(5) Patterns of use
Radio space is very limited, with demands on it from many different users, so that only a small range of frequencies is available in each country for cellular telephones [D].
Each hexagonal cell has a base station, which is assigned a portion of the limited radio channels available. All the channels are assigned over a pattern of 8 cells, and because the transmitters have such low power and therefore range this pattern can be repeated to let an entire country be covered with a small number of channels.
The number of local users determines cell size. Cells in a major city may be as small as 330 ft wide, enabling the available channels to be reused more often. The process of changing frequencies as a user crosses a cell boundary during a call is highly complex, and involves more unheard radio traffic between computers.
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The base station at first dealing with the call constantly monitors the strength of the phone signal [1]. As the user walks or drives away from the base station, the strength of the signal from his phone decreases. When it falls below a critical level, the base station sends a digital message, alerting the central exchange [2], which instructs nearby bases to measure the strength of the signal reaching them. The exchange then tells the phone to return to a channel on the cell receiving the strongest signal [3], and the conversation is resumed [4].
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