Screen: Handfree 4" CRT Panel: plastic material  Intercom: Among monitors in one house Expansibility: Up to 8 Monitors in one house, up to connect 4 cameras by MDS (4 way cameras switchers) Compatibility: Can work well any model outdoor camera  Melodies: 15 pieces melodies can be selectable as favor ring  Power Supply: DC 15-18V (Supplied by Adaptor) Consumption: Standby 0.5 W: Working status 15W (For kits) Wiring: 4 wires in polarity Distance : 50m when RVVP 4*0.3mm is used Video signal: 1Vp-p,75ohm,CCIR standard Audio transmit: Full duplex  Monitor timing: 30 seconds Talking timing: 90 seconds Dimension:226X191X53mm