4 channel h.264 dvr Video Compression:H.264 support VGA, HDMI ... and USB2.0. Support SATA HDD&USB disk RS485 PTZ controller Model4CHVideoInput4 channel ... 75?), 1 VGA, 1 HDMIAudioInput4 channel, BNC(200-2800mV, 30KΩ)Output1 channel, BNC(200-3000mV, 5KΩ)DisplayDisplay Split1 ... 1 for backupRS232Dahua keyboard, PC communicationRS485PTZ control 4 channel h.264 dvr