Very good indicator ...

I used this detector for several years in the house. However, I was of the opinion that three pieces would happen, especially since one of the detectors after a few years the alarm no longer wanted to spark.
Who aufhorcht now let me tell you that I had 8 detectors in the house, of which only one then no longer quite wanted. Think that's ok!
Also the fact that the detector sparks on the commonly used 433 MHz frequency is not a disadvantage, since the detector may again adjust to individual channels within this frequency.

Only Ster "disadvantage" is that the detectors per year need a new battery about once because the detector itself short every 10 sec. With one another and synchronize !!! But what are a few batteries for their own safety or ??? Hint: I use the batteries of YES. I have thus far had the best experience and they are not expensive!