As the title suggests, really even a phone without a power supply. Very good simple phone with key features on board. Buy with me for my desk. For me buying decision clearly the this device brings all its functions without a power supply. I have here already read that it does not run on a telephone system and that it is not illuminated is. I can only say that 504 plant runs it at a Eumex no dropouts and on a desk illuminated by monitor or desk lamp by his big keys is very good to use. Excellent voice quality. Missed calls are listed and the time is still on it. Very good also the speed dialing keys (8, double belegtbar).