There is an interesting point that i would like to make regarding the sensitivity of a similar instrument using the same principle. (the buzzer and light) I have in my possession two spirit lights in one unit. One using red LEDs and the other using white LEDs using the same lens. The principle if it is something good, the white will glow and if it is something distasteful the red will glow. It was siting on my mantle piece at Newark as we were trying to plaay the film 'Starman' with Geof bridges. I am not joking......the red light came on up to 8 times in 10 minutes as we frustratingly tried to play the film. When it started, the device was inactive until the bid came on where he was trying to revive the dead deer on the back of a truck in a petrol station. Both the red and white lights came on simultaneously. The film played towards the end where Geof Bridges is taken up by a space ship and the wite light came back on. When the film ended the red light came on! You should have seen it...lol Normally it will not activate for perhaps an hour or more I will play Close Encounters of the 4th kind and you can watch it yourself sometime!