Telenet Corp., a Washington based data communications network operator, is in the midst of an initial offering of stock to the public.

Incorporated in 1972, Telenet pioneered on a commercial basis a so-called "packet switched" data communications service, which permits a wide variety of computers and data terminals to be linked for instantaneous use.

Telenet operates a nationwide network of switching centers linked by leased high-speed communications lines. Through interconnections with other carriers, Telenet also serves Canada, Mexico, puerto Rico and a number of countries in Western Europe.

Most Telenet subscribers are corporations or government agencies using the interstate network for intra-organization terminal-to-computer communications, according to vice president Stuart L. Mathison.

The local firm's initial offering consists of 625,000 shares of common stock at $9 a share, through a team of underwriters headed by L. F. Rothschild, Uterberg, Towbin. When first announced in September, the company had hoped to sell the shares at between $16 and $20 apiece.

Earlier this year, Telenet launched a major expansion, adding 38 cities where access to the company's network is possible. By connecting 85 North American cities, Telenet's Network provides local access for about 80 percent of the U.S. population.

Regulated by the Federal Communications Commission, Telenet's Network is used by colleges to share resources without the need to construct and manage a private network, by a life insurance firm that offers computer-based services to independent agents and by a bank to make data available to correspondent institutions around the nation, to cite a few examples.

Telenet began operating its data system in mid-1975 Datamation, and authoritative journal, forecast earlier this year that the Washington firm would be in the forefront of a world wide "communications revolution," establishing data transmission in parallel services with existing telephone and telex systems.

However, another local firm engaged in a similar business, Data Transmission Co., folded last year and filed a suit against the Bell System, alleging anti-competitive practices. Telenet says in a prospectus for its stock offering it "expects" to face increased direct and indirect competition from companies with vastly superior financial resources."

Mentioned specifically was American Telephone & Telegraph Co., from which Telenet leases most transmission facilities.

Despite growth of revenues from $126,799 in 1975 to $1.9 million in the first seven months of 1977, Telenet has experienced substantial losses of more than $8 million from its inception. Revenues are not expected to increase to a level where profits can be earned util 1979, the company states.

In 1978, Telenet is planning an increase in locations where access to its network is possible, using funds from the public stock sale. No dividends are expected for the "foreseeable future."

Principal stockholders of the company are consultants Bolt Beranek and Newman of Cambridge, Mass. (39 per cent prior to this week's offering); Bessemer Securities Corp., New York (20.5 per cent) and Bowne & Co., New York (16.6 per cent). About 1.3 million shares were outstanding before the public sale began.

Lawrence G. Roberts, a former Defense Department computer planner, is chairman of Telenet. Anthony A. Barnett, previously with Bunker Ramo Corp. for 14 years, became president of Telenet in March.