Light detector app.

I admit it. I am pretty adicted to acquiring apps for my IPhone. I've simmered down a little lately but, at first, getting apps was fun and interesting. I got one app for blind people called light detector. I guess others could use it but there may not be much of a reason to do so. I use it a little at home to try to figure out whether or not the lights are on or off. Sometimes I can see them but sometimes I can't. but, yesterday, I was volunteering and learning about how to use radio equipment at one of our local radio stations. You have to push different buttons to turn on different systems (microphone, computer, cd player, IPod, etc) When you pressed a button, there was no difference in the height of it or position of it if it was on or off. I suddenly thought of my light detector app. The app has a tone which gets higher and higher the brighter something is. We turned all buttons off. I ran the phone along the row of buttons. There was a low beep that was continuous. Then I turned one on. Ran the phone along the row of buttons and suddenly a high squealy noise. I was amazed. Now something else I can do independently.