Simon Cowell's new reality series Duets has been given a six-week run by FOX as part of its Fall schedule.

The format - exec produced by, but not starring, Cowell - pairs professional singers with vocally-challenged celebrities in a traditional sing-off competition. The show will air on Thursday and Friday nights in a slot yet to be determined.

The show is one of a limited number of new series joining the network's schedule, which is dominated mainly by returning hits.

They include Prison Break, which will air the first half of its season before taking a break in January and returning in the Spring, and 24, which returns in January.

New series Vanished is teamed with the similar Prison Break on Monday nights, while crisis drama Standoff pairs with House on Tuesdays through January.

New comedies 'Til Death and Happy Hour take the 8pm hour on Thursdays, before The O.C. retains its tough 9pm slot.

Unscripted dominates Fridays, with Nanny 911 and Trading Spouses: Meet Your New Mommy each returning for new runs.

More: Click here for the list of returning and axed shows, here for a preview of the new series in the lineup and here for a night-by-night breakdown of the new schedule.