it works fine. the pitch should be higher. a little expensive. but it works all the time.

Can't really be concealed because it has to be in the open to detect motion. I tried to conceal it in a DVD cabinet between discs, but when the alarm goes off a light blinks and an intruder will be able to spot it easily and can turn it off in seconds. Not loud enough to be heard on a different floor and also goes through batteries quickly when left on.

Don't believe the description of this product. It does not have a loud 'alarm'. it is the same volume as the door chime and is difficult to hear through a door/window. I bought two of these thinking I could put them on a little used entrance way to provide some security against intruders- I think any intruders would laugh at the noise coming from this!