Allegheny County officials yesterday expressed confidence in their preparations for Tuesday's primary election, when voters will cast choices on new machines for the first time in a generation.

But officials also cautioned that the process of releasing results could take longer than usual. For this election, some voters will have the option of using fill-in-the-blank optical scan ballots, not the county's new touch-screen machines.

The county is deploying a dual-voting system to satisfy the federal Help America Vote Act, a law requiring local governments nationwide to update their aging voting technology.

Heavy demand across the county for new equipment has limited the number of machines available from Nebraska-based Election Systems & Software Inc. So far, the company has delivered 2,628 iVotronic machines to Allegheny County, two for every voting precinct. If a precinct attracts long lines, voters will have a chance to use paper ballots, which will later be read by a scanner.

By November's general election, the county will have 4,700 touch-screen machines and it will no longer use optical scan ballots.

The county's elections division has printed about 500,000 ballots for Tuesday, but officials can't predict how many will be needed.

"It's the big unknown on Election Day," county Chief Executive Dan Onorato said.

A light turnout, typical for primary elections, may ease demand among the county's almost 880,000 registered voters. There are few competitive races on the ballot, which includes primaries for governor, lieutenant governor, both houses of Congress and the state Legislature.

Still, county officials say they can handle an unexpected surge in voter interest.

"Everyone will have the right to vote if they show up," Mr. Onorato said.

Ultimately, he wants voters to feel comfortable with the iVotronic, which likely will be in use for years to come.

As part of an exhaustive educational campaign, the county has mailed out pamphlets to more than 600,000 homes. Port Authority buses are also distributing pamphlets.

The outreach efforts have placed a special emphasis on senior citizens, who tend to vote in larger numbers and are more likely to feel uncomfortable with new technology.

Tomorrow, several iVotronics will be on display during a senior fair at Community College of Allegheny County's North Campus in McCandless. The event, which runs from 9:00 a.m. to 2:30 p.m., is expected to draw as many as 3,000 people.

For a complete list of demonstration sessions, voters can visit the county Web site at www.county.allegheny.pa.us or call 412-350-8683.

The Web site features an interactive demonstration of the iVotronic and a link to a polling place locator.

The county has held extensive training sessions for 3,900 poll workers. Another 1,450 workers will receive training by the end of the week. On Saturday, poll workers can attend a refresher course at the International Brotherhood of Electrical Workers Hall on the South Side, from 9 a.m. to 1 p.m.

The county also has completed a successful mock election at a warehouse on the North Side. All machines performed well, according to county Manager Jim Flynn.

During Tuesday's election, more than 250 troubleshooters will roam the county to provide assistance at precincts that encounter problems. About 57 of the troubleshooters have more advanced expertise on the iVotronic and can help fix technical problems.

During a senior health fair at the Galleria in Mt. Lebanon yesterday, Mr. Onorato himself showed some voters how to operate an iVotronic sitting behind a Ben & Jerry's ice cream stand.

After briefly fumbling with a device that loads the ballot onto the screen -- a task performed by poll workers, not voters -- he breezed through the choices, giving a simultaneous play-by-play on his microphone.

"It's pretty simple," he said. "Instead of pulling levers, you're touching."

Sara Crescini, 73, a poll worker in Castle Shannon, wasn't convinced. She said some of her friends are reluctant to use the new machines.

"A lot of us don't have computers," she said.

Mr. Onorato said some difficulties on Tuesday are inevitable. That, however, will give the county time to work out problems before November's election, which will feature high profile races for U.S. Senate and governor.

"Let's get the kinks out in May," Mr. Onorato said. "Then the fall will be easier."