Digital extension the ericsson dialog 4225 vision system phone is one of the top of the range digital phones for the ericsson telephone systems it is designed to fit to the digital extension on an ericsson system so if it was connected to anything else it would not function some of the ericsson systems that it will work on are the mx one and md110 bc12 17 programmable keys the dialog 4225 has 17 programmable feature keys that the user can set up to tailor their needs this