She was a rich, older woman in New York and the younger man with whom she was having an affair was employed at Westinghouse.

When the younger man walked out on her, she hired an army of Manhattanites and deployed them with rolls of dimes to man pay phones all over the city.

For two days, her hirelings jammed the Westinghouse switchboard until New York police traced the caper back to her.

That, to date, is believed to be the most expensive obscene phone call on record.

To the telephone company, any "annoying or harassing call coming from an anonymous source" is classified as obscene.

Two young writers, 25-year-old Susan Kennedy and 23-year-old Julie Evans have just spent two years researching a book on obscence phone calls which Doubleday is dickering to buy from New York literary agent Mimi Strong. Among their findings:

A professor in Minnesota dons a tuxedo before making his calls. A 69-year-old woman made all her calls in hotel lobbies to guests registered upstairs.

Kennedy and Evans advertised in newspapers in New York and Minneapolis, inviting obscene phone callers to call them. They wrote their phone numbers in telephone booths and had them scribbled on men's-room walls.

More than 20,000 people were surveyed.

There will be an entire chapter on celebrities and public figures.

According to New York police files, Jacqueline Onassis, Barbara Walters and Woody Allen are among those who have complained to authorities about calls.

For those who can afford it, a company called Communications Control Systems in New York makes an electronic voice mask that sells for $3,000. It changes the pitch and timbre of the voice and can make Jackie Onassis sound like Muhammad Ali.

Sen. Howard Baker may be running the tighest ship in presidential politics. Retired admiral Stanley Fine, who ran the Navy's secret "Glomar" budgeting at the Pentagon, is watching every penny Baker's aides are spending. All but three telephone credit cards have been recalled. The candidate got to keep one of those . . . c

Contrary to a published report, Rep. William Moorhead's (D-Pa.) son, Billy Jr., is not withdrawing from the race to fill the congressional seat his father is vacating. Joy and Bruce Sundlun will give young Moorhead's first fund-raiser tonight with some of the Moorhead's most socially prominent friends on the committee. Supporters include Susan Mary Alsop, Evangeline Bruce, Pamela Harriman, former representative and Mrs. James symington and the Russell Trains. . . .

A New York moving and storage company with a large Iranian clientele says that their storerooms are bulging with Persian carpets. The Iranians apparently shipped them out in the final days of the shah's regime the way political refugees flee other countries with gold and diamonds.