1. Intercom function. Talk back from door station to monitors and monitors to door station. 2. High-performance CCD camera (CMOS camera optional), with infrared illumination to easily identify visitor even at 0.1Lux. 3. Noctilucent keyboard. Individual unlocking control circuit ensures the reliable unlocking. 4. Up to 4 monitors can be connected with the door station. Colorful or Black/White system is selectable. 5. Various kinds of general color or Black/White displaying could be selected for monitors. 6. Dual conversation between door station and monitor. 7. Monitor function is optional as follows: a. CM-06DRH(MEMORY); b. CM-06DRH(POWER IN); c. WL-06DRH(AUDIO PHONE). 8. Power supplier: adapter plug-in.