Using a unique modular design concept, US2002 user stations can be configured in numerous ways to suit virtually any application. User stations can be combined with power supplies of different types to form a host of master station configurations, or can be used without a power supply so that users can access multiple intercom channels with all of the features of a master station. User stations can also be combined with expansion station, like ES4000A and EMS4001, for access to even more channels. All functions of the user station are preserved for all intercom channels by linking the ES4000A (s) to the US2002 via a convenient, Ёы-inch, rear data connector. headset and/or speaker/mic operation for all intercom channels is accessed through the US2002 Master Station. Can operate in an unbalanced mode to be completely Clear-Com compatible.