DECT is botch, the rest works great

Since December 97 7270 my previous modem and the wireless router replaces.
Actually, the Fritz box should also replace the DECT base station, but AVM has so far failed to provide an interference-free DECT connection via firmware update. From about 4-5m distance a conversation (one has fear of tinnitus) by loud crackling hardly possible, either with extra purchased Fritz! Fon, even with existing Siemens Gigaset handsets. Simply abysmal! Too bad, because the Fritzbox else works great. Since already eight months (!) Have passed since the launch, the box will probably never hammer out a trouble-free DECT connection ...