I bought this phone to replace a faulty Fritz!Fon C5 phone which connects to my Fritz!Box 7490 Modem/Router. I have found the Fritz!Fon C5 phones to be quite unreliable. They die after a few years. It takes awhile for this Gigaset A540 phone to register with the modem/router. You have to hold the button down for quite a long time till it registers. But once registered it works well. Only problem, it is not compatible with the Fritz!Box Phone Book, so I cannot get all my phone numbers stored in it.