Hi,
You remove your handle from the door you want to secure then place this digital handle into it, it's retro fit.
Then you setup a Master password that you make sure to remember, (you can replace it at anytime).
You setup a user password between 2 to 10 digits using the numbers 0 1 2 3 4 5.
You can activate or deativate the noise of when you touch a number, same with the LED light but better keep it ON.
When you receive a guest you tell them the user password that you preset and tell them how to replace it if they which, by pressing from inside the door a small button under the handle then entering twice the new user password. No need to know the previous user password to replace the user password.
The master password still the same so you can always open the door.
The batteriesare on the inside door handle so no one can play with your nerves by removing the batteries. When the batteries are low the handle start to make a sort of christmass sound when you open the door.
If it's totally flat you still can open the door using a 9V battery on the external handle as their is two small connector for that purpose.
Battery is about 18 months. I'm using my handle since 3 years, never had any issue, it's amazing.