Although it didn't work for me in the end, it is a good product for its price at 20 euros. I have an old Urmet 4330 from the 70s and this one is only suitable for intercom replacement. There are 6 cables coming out of the wall, which are the microphone, speaker, buzzer, and lock. In the 752/33 model, an extra 12v AC buzzer is needed because the old model does not support it. The Rz cable will be connected there along with a bridge from the speaker cable. While if you have the 752/23 and switch to 33, no extra buzzer is needed. The detailed instructions are very positive.