... intercom 4.2 Channel 720P synchronous play back 4CH 720P recording NVR software Key features:Embedded Linux OSSupport 4 channel ... play back Item No.MI-N401-1UDevice4 Channel NVRSystemEmbedded LinuxFunctionPreview,recording,playback,back up,remote accessInterfaceOSD,1/4 screenLanguageChinese,English, ... Working humidity90%. No condensationsize110mm×80mmWeight500g (1.1lbs) 4CH 720P recording NVR software