A laser warning receiver is a type of warning system used as a passive military defence. It detects, analyzes, and locates directions of laser emissions from laser guidance systems and laser rangefinders. Then it alerts the crew and can start various countermeasures, like smoke screen, aerosol screen (e.g. Shtora-1), active laser self-defence weapon with Laser dazzler (LSDW, used on Type 99 China main battle tank), laser jammer, etc.