63 x 5. 63 x 1. 75 inches, it won’t attract too much attention. On the top of the detector, there is a recessed zone on which resides an elevated button press to silence the CO/smoke alarm and hold it to test weekly, a CO/GAS indicator, a Power/Smoke indicator and four circular cut outs for the speaker. There are no other flashy design elements, such as a large LED light, so compared with other ‘smarter’ detectors, it may look a bit plain, but it does have everything one would expect from a smoke/CO/gas/fire alarm. 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.