As the presidential campaign picks up steam and Election Day inches closer, officials in Centre County are getting anxious. They have not yet received the voting machines they will need come Nov. 4, let alone trained poll workers on how to use them.

The Central Pennsylvania county is switching voting machines after voters and county officials approved the change from electronic touch-screen machines to optical scan machines, which have a verifiable paper trail.

"This is going to be a tough election cycle for us," said Tim Boyde, the county administrator.

Centre County is one of many counties across the country that bought touch-screen voting machines to replace old paper-based voting systems in the wake of the election debacle in Florida in 2000.

After trying the touch-screen machines and seeing some of the problems associated with them and the lack of a verifiable paper trail, many counties decided to revert to paper-based voting systems, changing to optical scan machines in many places.

The decisions were driven by outcries from voting rights groups in some places. In three Pennsylvania counties -- Lackawanna, Northampton and Wayne -- the state decertified the brand of touch-screen machine that was being used.

With an optical scan machine, a voter marks a paper ballot, which is fed into the voting machine, which reads the ballot and tallies the results. In a touch-screen system, a voter touches a symbol on a display screen and the votes are recorded as data with computer software.

Changing voting machines is not a cheap proposition. In three states -- California, Florida, and Ohio -- the state governments last year ordered certain counties to change from touch-screen systems because of questions about their reliability and security or problems with the machine vendors.

As a result, counties across the country possess millions of dollars worth of decommissioned touch-screen voting machines, said Kimball Brace of Election Data Services, a Washington, D.C.-based consulting firm that tracks voting systems.

"The problem was that many jurisdictions were not patient enough to handle some of the initial problems with the touch-screen machines," he said. He noted that in many places, voting rights groups, which never liked the idea of touch-screen machines, were able to persuade local officials to switch to systems that leave a paper trail.

"It wasn't that the machines cost $5,000 apiece, but the cost of maintaining them as well was a big factor that led many jurisdictions to give up on touch-screens," he said. "The truth is, each voting system from the ballot box to the touch screen has its drawbacks."

In Centre County, Mr. Boyde said officials switched to a optical scan system after a well-organized group of voting rights activists campaigned against touch-screen machines.

"Personally, I was not in favor of changing systems, but there was a big groundswell in favor of optical scan machines," he said, adding that the issue helped two county commissioners get elected on that platform.

Unlike many counties that were stuck with warehouses loaded with useless and expensive voting machines, Centre County managed to sell back its machines to the vendor Election Systems & Software -- the company that won the contract for Allegheny County's touch-screen voting machines, the ES&S iVotronic.

"They initially offered us $100 for each machine, but we negotiated that up to $1,100 for each machine, but that worked only because we were going to buy the optical scan machines from them," he said.

The county sold back its machines to ES&S for $432,525, and will spend $1.2 million on the replacement optical scan machines.

In Lackawanna County, the 525 touch-screen machines cost $1.7 million, which will be reimbursed by the state, said Lynne Shedlock, a county spokeswoman. Now, the county will spend $1.3 million to buy new optical scan machines, she said.