-Designed to support up to 4 incoming telephone lines with 8 outputs/extensions per line used with ICRESVPAxx 8-port telephone compact module with RJ31X jack- Module is bridged as one expansion jack is used as input and the other one as expansion for more outputs/extensions by connecting to another ICRESVPBxx 8-port telephone expansion resi module- Fit all ICRESDC 14 21 28 and 42 Net Media Center