In my view Zwets comment about the power supply is the most likely cause, these can be very noisy devices.

Suggest you plug one of the power supplies into a different socket ring.

Keith..

Thanks for your help so far!

 The interference on the phone ranges from white noise to electronic sounding noise.  The router is upstairs and the phone was situated downstairs.

Are you really sure that the noise is caused by your router itself, in other words, if you have the white noise on the line and you then unplug the router, does the noise go away.

If yes also consider that your Netgear router is also connected to the phone line because it contains an ADSL modem, so do you have a micro filter on your phone line which the Beocom 6000 phone line plugs into. The microfilter could also be faulty.

White noise is going to come from a carrier on the phone line, whilst the BeoCom 6000's are DECT phones, the phone line is analogue which is why you need a microfilter on each of your phone lines in your home, otherwise you will have a problem.

Please check your microfilters

Keith..