These work very well; but 2 of them would not work. I have tried everything!
This is a really handy device for being able to program it remotely.
The devices were a little difficult to install because of the window frame, to align the arrows just perfect. The alarm is nice & loud! I feel so much safer now, especially when sleeping; however, 2 of the alarms did not work. It was a great bargain, low price.