For most District of Columbia voters, the system for casting ballots in Tuesday's special election will be unfamiliar.

Voters will not be handed paper ballots, and told to mark with black pencils the boxes next to the names of candidates. Instead, voters will get cards that they will punch with special devices.

Datavote, Inc., a California-based firm that manufactures the punch-card balloting devices, is hoping to demonstrate that its system will be more foolproof than paper ballots and will result in a faster, more accurate tally.

Under the trial system beign used Tuesday, each voter will get a ballot that is about as stiff as a Metro subway transfer, but has a format (with squares to be punched) like a Metro bus transfer. The card will include a numbered stub so precinct workers can be sure each voter is casting only his own ballot.

The voters will be directed to a booth, where there will be a small device with a handle that looks like a desk stapler and slides up and down on a short track. The voter will slip the ballot card into a slot on the left side of the device, then move the handle alongside the card until he reaches the name of each candidate he plans to vote for. After the handle is lined up beside the name of the candidate, a downward push on the handle will punch a hole in the card, thus marking the ballot.

A blank line is provided at the bottom of each list of candidates for write-in voting. Officials caution residents to cast only one vote for each office to be filled; otherwise, the ballot will be invalidated.

For most voters, the candidates for two of the three races-At-Large City Council and At-Large Board of Education-will listed on the front of the ballot.

Ward 4 voters will find candidates for that City Council race on the reverse side of the ballot. Voters in Ward 4 will slide the ballot out of the punching device after voting in the two at-large races, turnit over and vote for the Ward 4 candidate of their choice.

After completing the punch-card voting, a voter will slip the card into a "security shield" so precinct workers cannot see how the votes have been cast. A worker will tear off the exposed, numbered stub at the end of the ballot card and check to see that it was cast by the same person to whom it was issued. The ballot card will then go into the ballot box, to be counted later at a central location.