If you decide to do it yourself, the installation process is not really that difficult: first, you need to remove the mounting bracket by twisting the main body of the alarm, attach it to the wall and you will now connect the three wires from the wall to the Quick Connector as following: black to the hot side of the AC wire, white to neutral and yellow, if you need to interconnect with other existing alarms the Power has to be turned off prior to this operation. Afterwards, insert the Roost battery, plug the Quick Connector into the Roost RSA 400’s base, reattach the body of the alarm to the bracket and turn on the AC power. The green LED will indicate that the device is powered on and the red LED will blink once every 40 seconds to indicate a proper operation. The USST allows for an early smoke detection during stratification for both fast and smouldering fires using the same sensor for both and, in order to avoid false alarms, the device will operate at a low sensitive level and, in case smoke is detected, it will signal the alarm; it also adjusts and maintains a constant alarm threshold, therefore minimizing the effect of ambient conditions and it features a regulated 5V power supply for the ion chamber. If smoke has been detected, the alarm will beep three times, pause for two seconds and then repeat, the green power LED will turn off and the red smoke LED will start blinking once every second if smoke is detected by another interconnected alarm, the red LED will not turn on. Furthermore, if rising CO levels have been detected, the alarm will beep four times, pause for 5 seconds and repeat, while the power LED will turn off and the red CO LED will blink in sync with the 4 beeps the CO LED will stay off if the source of the emergency is in another room detected by another interconnected alarm. Lastly, if there are any gas leaks detected, the alarm will beep once, pause for two seconds and repeat, while the Power Led will turn off and the blue GAS LED will blink in sync with the once every–two seconds beep if the gas leaks are detected by another interconnected alarm, the GAS LED will not turn on. As a side note, the alarm should be tested weekly to ensure that it is working properly. The app user interface allows you to can add the Roost battery which is the smart part of the alarm to the app by tapping Add new and selecting Smart battery, choosing the location of the device, connecting to the local WiFi network and starting the setup process which will guide you through preparing the battery by pulling the tab, locating the speaker on your phone, turning up the volume and let the phone and the battery ‘speak’ to each other to establish the connection. Next, the app will let you know if everything is fine with your device and, by selecting the menu, you can configure the Profile, Change the Password, set up Invitations add other people, so they also receive notifications when the alarm gets triggered, read info About the device, Logout or Delete the Account. Also, by tapping on one of the installed alarms, you can check the Activity, view the Alarm Information, Change Location and Name, read Technical Information or Delete.