July 27, 1982

The American Home Products Corporation, the maker of Anacin and several other well-known consumer products, has agreed to purchase $250 million worth of advertising air time from NBC-TV over the next three years, the companies announced yesterday. The agreement, believed to be the largest forward commitment made by an American advertiser for television time, is apparently intended to shield American Home, the fourth-largest corporate spender on advertising, from rate increases over the next three years. The three major television networks are believed to be considering a 15 percent increase in advertising rates for the new season. The agreement, which would cover time in all parts of the broadcast day, is scheduled to begin this fall when the second of two contracts for two years between NBC and American Home expires.

A New York State appellate court yesterday voided the guilty plea of a Brooklyn dentist who admitted to sexually abusing an investigator posing as a patient. The court held that a videotape camera surreptiously installed in the ceiling of the dentist's office - and that had recorded the sexual abuse of the woman - had been put into place too long after the issuance of a warrant authorizing it. According to the appellate court, state law requires the installation within 10 days of the issuance of the warrant, whereas the camera in this case was installed 17 days after the warrant was issued.

The United States Government has begun a formal investigation into possible price fixing by six Japanese companies selling sophisticated semiconductor computer chips in the American market, Japanese and American Government officials said here today. The investigation by the Justice Department is focused on the practices of the companies in marketing 64K random access memory chips - the most advanced of the computer memory devices now available. John P. Stirn, a spokesman for the United States Embassy, said the embassy had notified Japan's Foreign Ministry of the investigation last Thursday. The six Japanese companies under investigation are: Hitachi, Nippon Electric, Toshiba, Fujitsu, Mitsubishi Electric and Oki Electric. They are Japan's largest makers of semiconductors, which are gridlike circuits etched on tiny chips of silicon. They are used for calculation and information storage, the basic functions of computers.

Two-thirds of New York City's poor people do not have home telephones, in part because of rising costs, State Attorney General Robert Abrams said yesterday. He added that 25 percent of all homes in the Bronx and 41 percent in Brooklyn's Williamsburg section did not have telephones. As a result, Mr. Abrams told a state Public Service Commission hearing, ''hundreds of thousands of New Yorkers must depend on neighborhood pay phones.''

IN another era, when society was firm in its view that automobile mechanics and plumbing were jobs for men and cosmetology and secretarial work were jobs for women, the public schools set up systems of vocational education reflecting these divisions. Now, however, as the presumption of segregating careers by sex has lost favor, the schools are under pressure to change those systems. The impetus is not only the demand for equal treatment, but also the fact that traditionally male fields usually pay much higher salaries. The issue is perhaps most sharply focused in New York City, where the school system, with almost one million pupils, is so large that entire high schools were created to teach a single trade.