The Alecto SA-19/5 is an optical smoke detector with a time-out button. This button is used to turn off the sound for 10 minutes. The smoke detector detects slowly smoldering fires and emits an audio signal of 85 decibels when detected. Insert the 9V battery in the detector and install it anywhere in the house. With normal usage, the battery lasts up to 5 years, so you won't need to worry about that for a while. Test the smoke detector regularly via the test button. That's how you make sure it's still working.