Quite a good first contact, I placed the transmitter with the double-sided tape it came with (hopefully it will hold) in the hallway of the apartment building and the receiver about 5 meters away. It picks up with a difference of 1 second, which is quite okay. The only thing that bothered me is that the melodies it has are incompatible (some Christmas tunes and chirping!!!), except for one option that I kept.

Strong ringing with many melodies (even Christmas ones). It captures incredibly well without being affected by distance or obstacles.