Harte, 33, has signed a two-year contract to move from the League One side Carlisle United.
He made his name as a left-back, most notably for Leeds United, but has played mostly as a centre-back for the Cumbrians.
Khizanishvilli, a Georgia international, has joined on loan from Blackburn. It was not only incoming transfers that kept staff at the Royals busy: midfielder Gylfi Sigurdsson, who scored against the Iron on the opening day of the season, moved to the German side Hoffenheim for £6million.
Striker DJ Campbell has made the step up to the Premier League, moving from Leicester City to Blackpool for an undisclosed fee. Campbell, 28, spent part of last season on loan at the Seasiders - helping them win the Championship play-offs.
"I'm over the moon, I'm delighted. It feels like I've got unfinished business, everyone knows how much I love Blackpool," he said.
"I wanted to come back and I'm just delighted that it's been made possible."
Leeds United have signed midfielder Adam Clayton from Manchester City.
Watford have allowed midfielder Scott Severin join Dundee United on a free transfer, after failing to make an impact at the Hornets in his season and a bit at the club.