Special Features: 1. 4" B/W CRT 2. Talk + Monitor + Unlock 3. Waterproof and prevent dust design 4. Plastic camera 5. Video and two way intercom 6. Unlock monitor Specifications: 1. Power course: DC16V 2. Screen: 4 Flat CRT 3. Min.Luminance: 0.5Lux \F2.0 4. Environmental temperature:-30 centigrade- 55 centigrade 5. Wait consume / operation consume: 1W / 13W 6. Effective resolution: 420 lines 7. Ring way: Ding dong ring or Chord are optional 8. External dimension: Monitor: 225L*170W*52H(mm) Camera: 152L*94W*31H(mm)