Addendum: The headset I use now been 5 years without cable break. Unfortunately, I eventually lost the protective foam. Thus, the small holes have clogged with dirt. This resulted in a low volume during calls. The small holes have now been cleaned and a new foam was placed over the fortuitous. Now I can hear very well my interlocutors again.
In addition, the headset was tested once on a Panasonic KX-TG8051 Dect phone. Unfortunately, the headset microphone was here too quiet for my interlocutor.