SITC of Central Control Unit for control of all microphones. The Control Unit shall include features for managing the number of active microphones and determining the operating mode, without the need for a central operator.It shall be possible to control up to 150 delegate units and power up to 50 delegate units.It shall be possible to connect external equipment to extend the system capabilities like External recorder, microphones, audio equipment, public address system,telephone/video coupler, language interpretation system. The Control Unit should have Microphone-mode switch for selecting one of four modes (plus test mode): Open mode, Open mode with auto switch off, Override mode, Chairman only mode. Rotary loudspeaker volume control for setting the output level of loudspeakers of contribution units. This control shall also determine the maximum level for the headphone outputs of contribution units and CU. The CU shall have built-in monitor loudspeaker and headphone socket allow the conference to be monitored