Digital extension the ericsson dialog 4222 is the second model up in the dialog 4000 range of digital telephones all the dialog phones will work with the majority of ericsson systems including the ericsson mx one md110 bc12 and the md110 bc11 telephone systems if you are not sure what your system is though a quick way to find out is by looking at what you existing phones are if they are either the ericsson dialog 4220 4222 4223 or 4225 then it will be fine display scr