The electric pencil sharpener whirred non-stop as jittery contestants readied themselves for the next round.

At the familiar signal, "On your mark. Get set. Go!" more than 170 people lunged forward in their chairs, flipped over sheets of paper on the lone tables before them, and settled down to work.

As the big clock at the front of the room ticked away, the contestants feverishy marked letters in tiny empty squares.

So, with a rush of silence disturbed only by the steady rubbing of erasers, the second annual American Crossword Puzzle Tournament got under way. Veteran puzzlers from as far away as Canada and South Dakota, even California, competed for the $250 first prize.

Interest in such competitions is evidence, puzzle experts say, that crossword puzzles are experiencing a resurgence in America, and now more than 30 million Americans are doing them. Puzzles appear in newspapers and magazines around the world, and in most languages.

"It's something you do on Sunday morning in you bathrobe instead of going to church," said Cecelia Roberts, a puzzle fanatic from Sioux Falls, S.D., during a break in the Stamford contect.

"I really envy people who live in big cities where they can get the best newspaper puzzles," said Roberts, who has a Ph.D. in medical sociology and teaches at the University of south Dakota School of Medicine. She took vacation time to drive to Stamford for the two-day puzzle contest sponsored by a local hotel.

Everyone works crossword puzzles somewhat differently. Some start at a corner. Others plunge a wherever they first find a word. Most use a pencil with a good eraser, but the supremely confident mark their puzzles in ink.

Some puzzlers slide through smoothly but others snap pencil points in despair after tussling with the light word for mosaic gold (ormulu) or mortise mate (tenon).

Helen Moran, who works for a New York antique dealer, has worked crossword puzzles for at least 30 years.

cAt home I do it lightly in pencil and then erase it and my husband does it later in ink," she said.

Few people are better able to judge the increased interest in crossword puzzles than Margaret Petherbridge Farrar, 82, editor of the first crossword puzzle book in 1924, and first crossword puzzle editor of the New York Time, a post she held from 1942-69. She is considered the grand dame of the American crossword puzzle.

"There's no question that there is a very real revival in every aspect of crossword puzzles," she said. "One signal is these contests which are going on more and more all over the place. It has become the thing to do."

But Farrar takes less comfort in other reasons that she believes have sparked the current crossword puzzle popularity.

"I'm afraid it's because these are hard times and people are worried," she said. "Doing a puzzle can rescue you from other problems. With a crossword puzzle you worry about that what 'seven down' is, and when you find out, you feel very intelligent and pleased with yourself. They have some therapeutic and psychological value that no one has measured."

Despite the current revival, puzzle experts doubt today's interest will ever match the puzzle-mania that permeated the United States soon after the first crossword puzzle was introduced.

English-born Arthur Wymn is credited with first putting the idea on paper on Dec. 21, 1913. After searching for a new idea for the puzze page of the old New York World's Sunday magazine section, he created the first puzzle-called word cross-with the word "fun" at the top. Persuaded by delighted readers to continue, the crossword puzzle soon became a regular feature of The World-the only U.S. newspaper to regularly print a crossword puzzle for more than 10 years.

The next major development came in 1924. One cold January evening a young literary enterpreneur named Richard Simon was having dinner in New York with a favorite aunt who ask where she could buy a book of these puzzles for her daughter.

There were no crossword puzzle books at the time, and publishers and book stores showed considerable skepticism for the idea. But Simon and Lincoln Shuster, partners in the new publishing company called Simon and Shuster, decided to put one out. They soon printed the first crossword puzzle book, but used another publishing company name because colleagues persuaded them that failure could doom their career.

The book, however, was an instant success. Simon and Shuster is now up to puzzle book no. 118. Margaret Farrar still edits the books.

Most of the rules for creating puzzles are the ones Farrar set down more than 55 years ago. Two letter words are out. No more than one-sixth of the square can be black spaces. Words about death, disease and taxes rarely appear. Designs are usually symmetrical.

Occasionally puzzle constructiors make mistakes, even Farrar. In a syndicated puzzle in February, Farrar placed placed Disneyland in Florida (it should have been Disney World).

"It was a horrendous mistake, and I'm still getting letters about it," she said. "A puzzle constructor has to be 100 percent correct."

There were no mistakes in the seven puzzles that competitors had to do at the recent Stamford contest. Each puzzle had a time limit-from 15 minutes to an hour.

Miriam Raphael of Port Chester, N.Y., who teaches English as a second language, finished the last puzzle in 18 minutes to come up with the first prize.