My 9500i has always alerted to every burst, I love it. I was driving along and I got a KA burst then it went away. About 1/2mile down the road was 3 LEO's running a speed trap in a school zone. Well I was sitting at a light and this cocky looking dude thinks i wanna race.. well he takes off all fast and then boom KA blast and he was tagged and one of the LEO ran to his car and chased him down and pulled him over.. It was funny.. But seriously, I have not had one instance where my 9500i alerted and it was to late. I alway have time to slow down and then see the LEO.. I dont know if this is luck ,or the 9500i is just a great detector.