The DC voltage of the power supply is superimposed by a strong AC component. Here does not help the integrated choke in the 12V line. The result is a 50 Hz hum when making calls. Consequently, the power supply to replace the Fritzbox is absolutely unsuitable and therefore not recommended! Become the part, not to be used as send back. Only after a long wait was referred back by AVM ISDN and the return for the non-functioning part I can then also bind to the leg.