The central control unit TC-ZB1 is the control monitor with the power supply. It controls master, treble, bass volume level and has three microphone modes. There is also a capability of recording the meeting speeches. It has also a DIN connector for addittional extension unit, RS232 port for computer control and RS 485 port for dome camera. The system can handle up to 60 delegate units and 5 intepreter consoles (and can be extended to delegate 200 units with addittional extension units).