Call force-through is not necessary with the Standard and Komfort home stations with receiver. This is because there are fundamental differences in speech transmission between the home station with hands-free function and a home station with receiver. The home station with hands-free function uses what is known as an echo suppressor. This means that, in voice mode, there are two voice ICs working together (1x in the home station with hands-free function, 1x in the door station). The voice ICs detect when speech is transmitted from the door station. The microphone pathway of the home station with hands-free function is muffled. In this case, in order to force the call from the home station through to the door station, you need to exceed the preset volume level. Normally, this is not an issue as, during a call, the person at the door has finished speaking before the person in the house answers. However, this becomes problematic if the person speaking at the door station has finished but the background noise (e.g. car noise) is so loud that the noise level does not drop sharply. As the microphone pathway is still considerably muffled in this case, the person at the home station must speak significantly more loudly for their call to go through. The force-through function helps here; it technically cancels the microphone pathway muffling and allows you to easily force the call from the home station through to the door station. This function is not required in home stations with receiver as the microphone circuit is not muffled in this way. For the version with receiver, it is fundamentally easier to force through a call from the home station to the door station, even if there are loud background noises.