Carlsile have signed Derby midfielder Paul Thirlwell for an undisclosed fee. The 27-year-old has joined the League One side on a full-time basis after spending three months on loan with the Cumbrians earlier this season.
Thirlwell joined Derby in August 2005 from Sheffield United but made only 17 starts, with six further substitute appearances for the Rams.
Carlisle signed Thirlwell on loan in September and he appeared 16 times for the club during that spell.