The RTS Audiocom EMS4001 Master Station Expansion Panel connects seamlessly to the MS2002 or MS4002 Master Stations to increase the number of discrete intercom channels from two up to 22. All functions of the Master Station are preserved for all intercom channels by linking the EMS4001(s) to the MS4002/MS2002 via a convenient rear data connector. Headset and/or speaker/mic operation for all intercom channels is accessed through the MS2002 or MS4002 Master Station. Can operate in an unbalanced mode to be completely Clear-Com compatible.