I inherited these two sound triggers from a good friend who photographed shuttle launches for an international news service. I have no idea of their condition, but you can see that one of the timers is still running on it's old batteries. I assume that they are placed a safe distance from the launch site; the timer is activated to wake up the system, shortly before launch time; then the camera if fired by the sound of the rockets closing a trigger circuit. Sold as is. No returns.