The Fostech Echo Trigger allows the shooter to select from 3 different settings: Safe Mode: Firearm will not fire. Semi-Automatic Mode: Firearm fires when trigger is pulled. Echo Mode: Firearm fires when trigger is pulled and also when trigger is released. The Echo Trigger is designed with safety being the utmost priority. When the shooter is in the Echo Mode and depresses the trigger one round is fired, if the target moves, the shooter can move the selector to the safe position and a second round will not fire upon release.