The MCS-D 3643 system unit has been designed for “under the table installations” in conference rooms. The MCS-D 3643 provides different connections to connect external components such as buttons, a gooseneck microphone and loudspeaker via 5-pin or 7-pin Phoenix terminals and a 5-pin XLR connector. By using the Lemo sockets the MCS-D 3643 is connected to the MCS-D 200 control unit or an external CA 4146 power supply unit. The MCS-D 3643 can be used as a chairman unit with microphone, clear and priority buttons or as a delegate unit with one microphone button. The microphone button is used to turn the microphone on or off. By using the priority button the chairman can interrupt the discussion and mute all activated delegate microphone units. By using the clear button the chairman can turn off all activated delegate microphone units. The system unit is powered via the bus cable and can be placed anywhere in the bus network. The operating mode of the microphone unit is configured via the MCS-D 200 control unit or the iCNS software. In the standard mode (free switching on) the participant can use the microphone button to switch the microphone on or off. In the request-to-speak mode the microphone button is used to enter a request-to-speak. The delegate can deactivate the requestto- speak by pressing the microphone button once more. In the automatic mode, the participant’s request is registered once the maximum number of active microphones has been exceeded. If a participant switches off his/her microphone, the microphone unit is switched on automatically. In the FiFo (first in - first out) mode, the delegates speak in succession. The delegate can use the microphone button to switch on the microphone. If the maximum number of open microphones is exceeded, the microphone of the speaker who has been speaking the longest is switched off.