Bite alarms are devices that emit an audible signal when the fish gets hooked and starts running off. You use reels that have whats called a baitrunner. Turn it on and then when something pulls on the line the spool turns in reverse and lets line out at a controlled pace with the bail closed. You set the rod in the bite alarm with the line laying across a wheel in the bite alarm. When the fish starts pulling line out the wheel spins and sets the audible signal off.