NikKTech reviewed the AVM FRITZ!Fon C4 & C5 DECT Cordless Telephones
A quote from the article:
FRITZ!Box DECT Modem/Router owners out in the market for a new cordless telephone should look no further than the FRITZ!Fon C4 and C5 models not only because of their crystal clear audio quality, good signal strength, excellent battery life and 180ppi color LCD screens but also because of their wealth of software features.AVM FRITZ!Fon C4 & C5 DECT Cordless Telephones Review