Americans will make close to 1 billion phone calls to foreign countries this year, feeding a worldwide boom in cross-border dialing that with little attention has driven volume up fivefold during the last decade.

Most of the calls will carry business conversations or the electronic signals of the facsimile and computer generation. But more and more, ordinary people are picking up the phone and dialing around the world just to gab. When all these calls are added together, they become a $30 billion-a-year business.

While other facets of the much-heralded "information age" have failed to pan out, on-demand phone communication to any part of the world is steadily coming true.

It is now possible to dial from a car traveling on Interstate 270 to a car moving through downtown Tokyo. Even Albania, long one of the world's most isolated societies, now has direct-dial service with the United States.

In 1990, international callers will spend about half a billion hours on the phone, according to a study by the London-based International Institute of Communications (IIC). Gregory C. Staple, the study's author, predicts no slowdown: "There's no reason to believe that 15 to 20 percent growth will not continue through the '90s."

The boom has given rise to a new discipline of sorts, "tele-geography," the study of patterns of who is talking to whom and why. Heavy calling from the United States to the United Kingdom (it is the second-most-called country for Americans after Canada) probably reflects close economic and political links and the common language. Heavy calling to Colombia (it ranks 10th) reflects immigration, business ties and, probably, the cocaine trade.

Not a few people feel that phone lines have helped in a major way to spread Western ideas in the communist world and feed the democracy movements there. People in China, once all but closed off from foreign contact, were taking about 10,000 calls a day from the United States before the Tiananmen Square uprising.

Dennis Patrick, former chairman of the Federal Communications Commission, suggests: "The more interaction in communications there is, the more various persons in various countries can compare and contrast their systems."

New technology helped set the trend in motion. U.S. telephone companies installed direct-dialing equipment in the 1970s, and much of the world followed. In the '80s, the Intelsat communications consortium launched progressively more powerful satellites into orbit, increasing the number of circuits available and improving line quality.

Late in the decade, long-distance companies switched on the first fiber-optic transoceanic cables, which employ the high-capacity "digital" technology of computers. One cable that runs 4,600 miles across the Atlantic Ocean floor measures less than an inch in diameter but can carry 85,000 calls -- as well as video and data transmissions -- at once.

"The completion of those oceanic cables was a historic moment that nobody recognized," said Bill Davidson, a professor of international business at the University of Southern California.

A trend in the industrialized world toward competition in what had traditionally been a monopolized field helped things along by lowering prices (though the business remains highly profitable) and bringing in new types of services.

The breakup of American Telephone & Telegraph Co. in 1984 cleared the decks for MCI Communications Corp. and US Sprint Communications Co. to take major shares of U.S. overseas traffic. Britain now has two international long-distance companies; Japan has three.

In the meantime, demand was growing fast. Companies and banks were rushing to go global and automating their in-house information by putting it into computers. Companies handling engineering of products in one country, manufacturing in a second and sales in a third needed ways to talk or transfer data between the far-flung sites. Many chose phones, often setting up their own private networks.

Reliable long-distance connections have begun to allow service jobs to be dispersed around the world as well, giving the companies access to lower-paid work forces. U.S. computer companies have software written in low-cost India and sent to the United States by satellite. American Airlines flies ticket stubs to the Caribbean island of Barbados daily,where keyboard operators punch the information into computers and send it back to the United States electronically.

Having communications at one's fingertips helped fuel the creation of world markets for securities and foreign exchange, which in turn spurred a need for more communications. Traders today turn to whatever market is in operation when customers call.

Mass adoption of fax machines in the late 1980s set off further growth, especially on transpacific communications. About half of all phone calls across the ocean today carry not conversations but fax transmissions. In 1989, the IIC found, the approximately 3 million fax machines in Japan had generated as much international calling as the country's 49 million telephones.

With business calling growing fast, long-distance companies are hoping to get ordinary people into the act, too. US Sprint, for instance, allows Japanese tourists holding their country's popular JCB credit card to bill calls home on the Sprint network. MCI has a discount plan that connects a caller to Europe for less than 60 cents a minute. AT&T has targeted Filipino residents of the United States with special cut-rate calls to the home country.

It has reached the point where about 2 percent of all calls placed in the United Kingdom go abroad. The figure for the United States is about 1 percent. Japan's figure is growing too, but offers evidence of its society's continuing insularity: There, according to the IIC, only about 0.15 percent of all calls are international.

One reason that Japan's rate is so low is lack of common language with foreigners. Japanese computer scientists are working on a solution to that, however: in labs they have built prototypes of systems in which Japanese spoken into one phone would come out as English at the other and vice versa, translated by advanced computer software.

Another region that is behind: the Soviet Union and Eastern Europe. Their newly liberalized governments are shopping around for better communications equipment, viewing links with the outside world as crucial in the quest for prosperity and foreign capital. The Soviets have about 35 million phone lines but generate fewer foreign calls than many countries with a tenth of that number.

The common wisdom is that more communications between countries can only be for the better. But in at least one field, the trend has created a new set of international tensions, over payments that phone companies make to counterparts in other countries for completing calls. The United States now shells out far more than it takes in -- the shortfall was about $2 billion in 1988 -- creating an important new splash of red ink on its balance-of-payments sheets.