Used for entry to office. Handy when office staff is light. Receiving unit plugs into wall outlet - no power problem there. Sending unit w/ infrared motion sensor runs on 9-volt transistor battery. Expect to change battery once or twice per year without any notice. We mounted it to a wall with Velcro tape because it needs to be removed and flipped over to remove battery cover to change battery. Has about 30 different alert sounds, although ding-dong seemed best for us for professional office. If we need more, will buy again.

So easy to use. I put it on the floor near the front door and plug it into the back room. This way I know when some one comes in the front door. Awesome.

Still trying to adjust, but it does go off occasionally with out provocation

Does the job, good range

works good very satisfied