Imagine casting your vote on an everyday touch-screen tablet that prints out a paper copy of your ballot, as well as a take-home receipt you can use to verify it was counted. Such a system could be in place at Travis County polls as early as 2017. For the past three years, the county and a group of experts have been designing the specifications for new voting software that would rein in costs while providing what critics of electronic machines have long requested: a verifiable paper trail. “You can never win the argument over black box voting,” said Travis County Clerk Dana DeBeauvoir. Under the system being developed, a voter would use a device — likely a tablet — to fill out an electronic ballot and then print out a paper copy for voters to check. The electronic ballot wouldn’t be tallied unless the voter deposited the paper copy into a ballot box that scans a serial number printed on it. The voter would also receive a receipt with a code that can be entered online to confirm the ballot was counted.