Hi Zaheer,

That's not a stupid question! Normal analogue DECT phones are indeed compatible, how ever you will need to make use of an ATA adapter between the internet and the analogue phone. These devices seem to work fairly well:

http://www.miro.co.za/product/grandstream-701-sip-analogue-telephone-adapter-1-lan-1-fxs/

Essentially you need that device to load the SIP account on, the DECT phone will plug into the analogue port on the adapter and work like it was a SIP phone.