Review on AVANTEK Mini Waterproof Wireless Doorbell Chime - Operating at 1000 Feet with 52 Melodies, 5 Volume Levels & LED Flash by John Murphy

Well, honestly, I don't know for how long. However, for my purposes and for anyone reading this, this works as intended. That is, 1 is in the house and the other is in my shop (no less than a metal building. I plugged the phone into the socket in the right corner. It's about 3 feet from the door on the right). I tested several times with the phone recording by pressing the button. And as expected and as the name suggests - 100% working. I am very happy with it. If I dare guess, I'd say the distance (from the doorbell to the store) is over 60 feet. Hope that helps!