The control monitor is the power supply, the sound processor ,switch of the conference system. And it can be record the sound for the meeting. This control monitor must be used with amplifier,loudspeaker together. In order to make the sound better, this monitor should be inline with mixer or equalizer through the interface LINE OUT or BALANCED OUT or NO BALANCED OUT.1. Power switch 2. Ear to 19 standard machine cabinet rack mounting 3. AC220V 50Hz power socket 4. Units interface: can connect 50 units (25 units for each trunk) 5. Switch for selecting the speaking delegate units at the same time(3 or 6 units ).Thechairman units isn't be limited by this monitor. 6. Output record interface for recording the meeting. 7. Balanced output8. Unbalanced output