When the U.S. Postal Service asked for bids several years ago on $500 million in optical character readers to sort mail, it received an enthusiastic response, from foreign companies.

Of six proposals, all came from overseas firms, including two from Nippon Electric and Toshiba of Japan. The companies offered the latest in high-technology postal equipment capable of reading the zip code on letters, checking it for accuracy and marking each envelope with a bar code for sorting and routing.

There was a "lack of interest" on the part of U.S. companies which "just didn't have any machines that we wanted," said Assistant Postmaster General James French.

What was surprising was that much of the early work on optical character readers had been done in the United States.

Such examples of foreign companies capitalizing on technologies pioneered in the United States are far from rare:

Although the transistor was invented at Bell Laboratories in 1947 by Nobel laureates William Shockley, John Bardeen and W.H. Brattain, Japan's Sony first sold transistor radios in this country in 1956.

A U.S. company, Ampex, introduced the first videotape recorder, the Quad, in 1956. But Sony engineers, working feverishly to improve on early U.S. designs, preempted the American consumer market in videocassette recorders with the Betamax in 1975.

RCA and Philips pioneered the technology for color television. But by 1969, Sony's Trinitron picture tube and Hitachi's solid-state color receiver had put the Japanese ahead.

In 1969, RCA invented complementary metal oxide silicon (CMOS), a process for making microchips that use very little power. Some microelectronics specialists say Japan is now even with or ahead of the United States in such technology.

In the case of the foreign optical character reading equipment, the Postal Service resorted to "Buy America" tactics to make sure that U.S. companies got a piece of the new high-technology business. It agreed to buy the equipment, but only if it were made in the United States, and suggested that the foreigners acquire American "partners."

The contract was awarded to two U.S. companies, Burroughs and Pitney Bowes, which teamed with Nippon Electric and Italy's Elsag to make the character readers. The other companies dropped out.

"We went a little beyond 'Buy America' . . . . I suppose we did what Japan sometimes has done," French said. "But we're part of this country, and its economic health and well-being are important to us."