The ones in Knox County you have to dial in a 4-digit code before you vote. I don't know if that means that the machine can handle no more than 10000 votes in a day, but I'm guessing that it might. The code carries with it precinct information and such -- so if you live in Knoxville proper, then the city ballot proposals show up on your machine and if you live outside the city then only the county proposals show up. Also the correct US Rep, State Senator, and State Rep offices show up on your screen. So I don't know if the codes are stratified beforehand or during early voting.
Sounds like a different machine than is used here in the Chattanooga area. We don't vote on a machine, but simply feed the completed ballot into it. We get to fill out a paper ballot by coloring in the block next to the candidate/issue we choose after which we hand the card to the official, he tears off the numbered stub and files it separately, and then has the voter feed the voting ballot into the slot on top of the machine. Looks like a giant shredder, but it's merely an optical scanner of some sort.