Actually, good phone, but incompatible with 4x switch

I had an analog phone wanted that manages the power from the telephone line, ie no separate power supply is needed. In addition, it should still CLIP, speaker and some buttons have names - then there is no longer the number of devices to choose from. So I came up with the Gigaset DA710 that this has everything.
The order from Amazon was made quickly, delivery also, the connection worked right away.

Then I wondered, that always came calls, was launched in which after the first ring. The caller had then get a busy signal. Cause is the Gigaset DA710 that not so clear is the fact that the voltage of the telephone line behind the upstream with me quadruple switch is weaker than directly connected.
My three "ancient" Euroset 2015 phones work with it without any problems for many years.

After two mails the Gigaset Hotline has confirmed that all its equipment are (!) Do not switch compatible. In the documents which is but nowhere. Therefore, I see this review as a warning to all those who still have such an old switch.