In April 1995, a young Chinese chemistry student at Beijing University lay dying in a Beijing hospital. She was in a coma, and although her doctors had performed numerous tests, they could not discover what was killing her. In desperation, a student friend posted an SOS describing her symptoms to several medical bulletin boards and mailing lists on the Internet. Around the world, doctors who regularly checked these electronic bulletin boards and lists responded immediately. In Washington D. C. , Do, John Aldis, a physician with the U.S. Department of State, saw the message from China. Using the Internet, he forwarded the message to colleagues in America. Soon an international group of doctors joined the e- mail discussion. A diagnosis emerged -- the woman might have been poisoned with thallium, a metal resembling lead. A Beijing laboratory confirmed this diagnosis -- the thallium concentration in her body was an much as 1,000 times normal. More e-mail communication followed, as treatment was suggested and then adjusted. The woman slowly began to recover. Well over a year later, the international medical community was still keeping tabs on her condition through the electronic medium that saved her life. It's 11: 30 p. m. , you're is San Francisco on business, and you want to check for messages at your office in Virginia. First you dial in and get your voice mail. Next you plug your portable computer into the hotel-room telephone jack, hit a few keys, and pick up e-mall from a potential client in South Africa, your sister in London, and a business associate in Detroit. Before writing your response, you do a quick bit of search on the Internet, tracking down the name of the online news group you had mentioned to the man in Detroit and the title of a book you wanted to recommend to your sister. A few more keystrokes and in moments your electronic letters have reached London and Detroit. Then, knowing that the time difference means the next workday has begun in South Africa, you call there without a second thought. These stories reflect society's increasing reliance on system of global communication that can link you equally easily with someone in the next town or halfway around the world. The expanded telephone-line capacity that has allowed the growth of these forms of communication is a recent phenomenon. The United States has enjoyed domestic telephone service for more than a century, but overseas telephone calls were difficult until relatively recently. For a number of years after World War Ⅱ, calls to Europe or Asia retied on short-wave radio signals. It sometimes took an operator hours to set up a 3- minute call , and if you got through, the connection was often noisy. In 1956, the first transatlantic copper wire cable allowed simultaneous transmission of 36 telephone conversations -- a cause for celebration then, a small number today. Other cables followed by the early 1960s, overseas telephone calls had reached 5 million per year. Then came satellite communication in the middle 1960s, and by 1980, the telephone system carried some 200 million overseas calls per year. But as demands on the telecommunication system continued to increase, the limitations of current technology became apparent. Then, in 1988, the first transatlantic fiber-optic cable was laid, and the 'information superhighway' was on its way to becoming reality. Optical fibers form. the backbone of the global telecommunication system stronger, length for length, than steel -- were designed to carry the vast amounts of data that can be transmitted via a relatively new form. of light-tightly focused laser. Together, lasers and optical fibers have dramatically increased the capacity of the international telephone system. A typical fiber-optic cable made up of 100 or more such fibers can carry more than 40,000 voice channels. With equally striking improvements in computing, the new communication technology has fue