Missing, independent power indicator.

It's strange: if you want to know if the thing really works, you have to press the center button, and then is confirmed by the loud Siren Enge Piepe.
Sporry, but I can not live, and my pets.
The simplest CO or smoke alarm will flash once every 30 to 60 seconds on short and to show that they are ready and vigilant.
The argument that there is battery can be saved, I can not accept, because the week by repeatedly pressing
Siren is much wasted more energy than the very short blinking.
The frightened pets are an additional reason, which is the product unsuitable for me.
In addition, the operation with just two small AAA batteries m. E. interpreted too weak.

Conclusion: immature and too expensive for the cumbersome operation display, the detector returns immediately.
There is something dangled in the photos, which is not there so the detector is in continuous operation without any ad.